The Lyon Mint in the Roman Tomares Hoard (Seville): Some Considerations on Its Metallic Composition Determined by XRF

XRay Spectrometry, 2025; 0:1–10 https://doi.org/10.1002/xrs.3502 1 of 10 XRay Spectrometry RESEARCH ARTICLE OPEN ACCESS The Lyon Mint in the Roman Tomares Hoard (Seville): Some Considerations on Its Metallic Composition Determined by XRF RuthPliego1 | BlancaGómez-Tubío2,3 | MaríaAlcaide-Ramírez1 | SimonaScrivano4 | MiguelÁngelRespaldiza3,5 1Department of Prehistory and Archaeology, Facultad de Geografía e Historia, Universidad de Sevilla, Sevilla, Spain | 2Department of Applied Physics III, Escuela Técnica Superior de Ingeniería, University of Seville, Seville, Spain | 3Centro Nacional de Aceleradores, (Universidad de SevillaCSICJunta de Andalucía), Seville, Spain | 4Centro de Investigación Tecnológica e InnovaciónLaboratorio de Rayos X, Universidad de Sevilla, Seville, Spain | 5Department of Atomic, Molecular and Nuclear Physics, University of Seville, Seville,Spain Correspondence: María AlcaideRamírez ([email protected]) Received: 22 January 2025 | Revised: 14 May 2025 | Accepted: 29 May 2025 Funding: This work was supported by Ministerio de Ciencia, Innovación y Universidades, PID2022139617NBI00; University of Seville. Keywords: late antiquity| Lugdunum| numismatics| nummi| XRF ABSTRACT There is no doubt that coins are of great interest to historical research, as they provide a wealth of information about the period in which they were minted. The Roman Tetrarchy (AD 294324) was one of the most turbulent periods in Roman history. It was characterized by power struggles between different rulers, which were reflected in the reduction of the weight and fineness of the coins. The Tomares hoard, discovered in this Sevillian town in 2016, is one of the largest hoards from this period. This paper focuses on the analysis of the metallic composition of coins from Lugdunum (current Lyon), a mint of fundamental importance in the monetary history of the Roman Empire and one of the most important of the Tetrarchy. Out of a total of 2291 coins analysed since the beginning of the study of this hoard, nondestructive Xray fluorescence (XRF) analysis has been carried out on a selection of 227 coins from this mint of Lyon. The chronology of these ranges from AD 294 to 309, a period relatively unexplored from an archaeometric point of view. The results obtained, in conjunction with the numismatic studies, provide valuable information on the historical context, the alloy used, and, more generally, the behavior of this mint, helping, among other things, to establish the chronological seriation of its issues. This work highlights the importance of the Tomares hoard as a valuable source to characterize the Roman economy in the 4th century AD. 1 | Introduction The Roman Hoard of Tomares (Seville) was discovered on April 27, 2016 during public works in the El Olivar de El Zaudín park in this town and is currently kept in the Archaeological Museum of Seville. The collection is made up of 19 Roman amphorae intended to contain Betic oil, which were found to be filled with coins. Most of these amphorae were damaged by the excavator, but nine were recovered intact and remain sealed. On the basis of the information available to us, we estimate the total number of pieces in the hoard at 53,200 [1]. Recently we studied the tetrarchy mint of Carthage, in order to understand the relationship between this mint and the Iberian Peninsula [2]. In this work, the connection between the Iberian This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. © 2025 The Author(s). X-Ray Spectrometry published by John Wiley & Sons Ltd. 2 of 10 XRay Spectrometry, 2025 Peninsula and the Gallic mints is examined, using the Lyon mint as a case study. Measurements were carried out on a selection of 227 coins of this mint dated between AD 294 and 309. The results obtained from the analysis by XRay Fluorescence (XRF) for the nondestructive multielemental characterization of the coins provide information on the compositional changes of the issues of this mint, in particular some of the archaeometrically less known issues, such as the first issues from the First Tetrarchy. This may help in further work to establish the chronological seriation of its issues, especially in relation to the earliest and also the rarest of the repertoire known to date. On the other hand, it is proposed to study the successive devaluations of silver throughout the Tetrarchy, since, as we shall see, despite the claims of monetary stabilization aimed at by the reform of AD 294, the scarcity of the precious metal and the economic difficulties led to successive reductions in the weight and fineness of the coins. This has already been verified regarding Carthage, which was previously analyzed using the same technique [2], and it also allows us to compare the behavior of the Gallic workshop with that of this African city. 1.1 | Historical Contexts The historical context of the Tomares Hoard is the Roman Tetrarchy, established in 294 by Diocletian (AD 284–305). In this date Diocletian, in an attempt to stabilize the economy, undertook a monetary reform [3–5] establishing a complete system of monetary denominations and fixing the weight and fineness of the respective metals. This reform affected the values of gold and silver [6], but also introduced a new billon coin, the nummus—sometimes called follis in numismatic literature— which constitutes the Tomares hoard. Initially set at 1/32 of a pound, it debuted with a weight of around 10.75 g and a silver content of about 4%, both of which were reduced during the Tetrarchy, as we shall see. In contrast to the previous periods, there was a decentralization of monetary production, with mints being established in 16 cities in the new territorial circumscriptions, the dioceses. These were created by Diocletian as part of his reform of the territorial organization of the Empire to facilitate administrative management (AD 297) (Figure1). According to the Laterculus of Verona [7], the Iberian Peninsula formed the diocese Hispaniarum. Despite its undoubted strategic value in controlling the Straits of Gibraltar and its relationship with the diocese of Africa was probably considered a peripheral territory, and it was not assigned a mint at this time— the same applies to the diocesis Viennensis. The Lyons mint was one of the great mints of the Roman Empire, being the workshop with the largest bronze production of the GalloBritish mints [8–10]. The first issues date from BC 43, year FIGURE 1 | Map of the imperial mints and dioceses established during tetrarchy. [Colour figure can be viewed at wileyonlinelibrary.com] 10974539, 0, Downloaded from https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/xrs.3502 by Readcube (Labtiva Inc.), Wiley Online Library on [11/07/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 3 of 10 of foundation of the settlement, being established by Augustus as an imperial workshop for the production of precious metals year BC 15 [9] and continued until the time of Nero. Thereafter it had an intermittent activity until the victory of Aurelian over the Gallic Empire caused the workshop to reopen in AD 273. Later the activity was reactivated in the new monetary organization established by Diocletian and under the issuing authority of Maximian Herculeus, the first augustus of the pars occidentis of the Empire, with Constantius Chlorus as caesar. During the Tetrarchy, Lugdunum had two workshops (officinae monetalis), which appear on the coins in abbreviated form next to the mint mark (L)—sometimes preceded by the letter P, interpreted as Percussa or Pecunia [11]—next to the letters A (for the first workshop) and B (for the second). The arrangement of the letters in the exergue or field changes as the tetrarchy progresses, making it possible to establish the chronology of the issues within the large groups. One of the most striking features of the Lyon mint is that the issues of the first part of the period present some difficulties in terms of seriation, partly since the repertoire of some of them is very limited [4]. Following the Roman tradition, these coins generally show the emperor's portrait on the obverse, while the reverse is mainly occupied by one or two deities. The most common reverse design of the Lugdunum mint is that of the Genius, linked to the ecumenical vision of the Romanitas that Diocletian wished to show during the Tetrarchy (Figure2). Lugdunum has attracted the attention of researchers, and we even have a complete monograph on this mint by Bastien [9], with V. Drost's contribution to its numismatic clarification also being outstanding [12]. In addition to Bastien, other authors have carried out studies on the Lyon coins, such as Sutherland [4], Cope [13–15], Lafaurie [3], Callu [16], Bollard and Barrandon [17], and Hunt [18]. This has provided this workshop with a relatively large repertoire of metallic analyses compared to other mints of the Tetrarchy. However, within this repertoire, the number of coins analyzed for some issues is scarce or nonexistent, partly due to the aforementioned scarcity of some of the Lyonnais series. The availability of specimens from the Tomares Hoard largely solves this problem, with a total of 1776 coins so far, representing 12.42% of the total studied. 2 | Materials and Methods 2.1 | Conservation and Cleaning The coins analyzed were cleaned and consolidated as follows, although some of them were only cleaned mechanically to remove surface dirt: (a) they were first immersed in demineralized water with neutral detergent and then brushed to remove surface dirt; (b) to remove some of the corrosionrelated materials, particularly chlorides, they were immersed in pHcontrolled sodium sesquicarbonate; (c) some of these chloridecontaminated coins were stabilized using Benzotriazole (BTA) [2]. 2.2 | Coins Analyzed As mentioned above, the sample analyzed consists of 227 coins dated between AD 295–309. They are presented in Table1 in chronological order, with the characteristics of the mint mark and, in the last column, the number of coins in each group and issue, according to the reference works [4, 9]. It is worth briefly explaining the meaning of the distinction between groups and issues established in RIC VI, since it is related to the political circumstances that took place in the context of the Tetrarchy. Hence the interest of taking them into account in the analysis: • The five oldest coins in the selected sample belong to issue ii of Group I, dated AD 295, and are also the oldest coins from this mint in the entire hoard, as no coins from issue i, dated 1 year earlier, have yet been documented. This second issue includes coins from workshops A and B and their weights range from 8.5 to 10.75 g. • On the other hand, as can be seen in Table1, we have analyzed coins from issue ii to issue x, except for issue iii. The issue with the most coins in the sample analyzed is issue ix, with 94 coins dated between AD 301–303 (Figure3). The last mentioned is one of the issues with the largest number of coins produced, with different typologies in which FIGURE 2 | Nummus of Constantius I Caesar, mint of Lugdunum, AD 295 (10.06 g; 28.5 mm) (RIC VI, Lugdunum, 4a). Tomares Hoard, MASE DJ2016/0602302; ID 2302). [Colour figure can be viewed at wileyonlinelibrary.com] 10974539, 0, Downloaded from https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/xrs.3502 by Readcube (Labtiva Inc.), Wiley Online Library on [11/07/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 4 of 10 XRay Spectrometry, 2025 augusti and caesars are represented (cuirass, spears, helmet, club…) as can be seen in Figure3. After this date, the mint of Lugdunum had only one active workshop from issue x onwards. • The Group II's issues began in May AD 305, after the abdication of Diocletian and Maximian Herculeus as Augustus. Samples from seven different issues were analyzed, of which iv and vii are the best represented, with 17 and 22 pieces TABLE 1 | Seriation of the sample in chronological order, classification and cataloguing according to the reference works of Sutherland (RIC VI, 1966) [4] and Bastien [9]. Period Mint mark References N° specimens analyzed RIC VI Bastien Officina AOfficina BTotalGroup Issues 295 LA/LB Iii iii 1 4 5 296 Unmarked iv 2 297 LP va 1 298 A or B/LP via v8 3 11 298 A or B/PL vib iv 4 5 9 299 altar/A or B/LP viia vi 1 1 300 altar//PLC viii 1 301–303 altar/A or B/PLC ix viii 41 53 94 303–305 altar/*/PLC xix 17 305–307 altar/*/PLC II ixi, xii 22 TF//PLC ii x3 306spring 307 PLC iii xii 3 Spring 307 altar//NPLC iv xiii 16 Summer 307 TF//PLC vxv, xx 1 SC//PLC vi xvi, xxi 1 Late summer 307 N//PLC vii xvii 21 Autum 307 N//PLC- //N/PLC III ixxii 2 Autum 307summer 308 altar//PLCPLC ii xxiii 11 Autum 308spring 309 CI H/S//PLC iii xxiv 6 Total 227 FIGURE 3 | Nummus of Maximian Herculus Augustus, mint of Lugdunum, AD 301–303 (10.5 g; 27.21 mm) (RIC VI, Lugdunum, 115b). Tomares Hoard, MASE DJ2016/0601132; ID 1132). [Colour figure can be viewed at wileyonlinelibrary.com] 10974539, 0, Downloaded from https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/xrs.3502 by Readcube (Labtiva Inc.), Wiley Online Library on [11/07/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 5 of 10 respectively, as indicated in Table1. This group includes issues produced after the death of Constantius Chlorus in July AD 306 and reflects the problems that followed with the power struggles between Constantine and Maxentius. Not surprisingly, from issue iii (AD 306–spring of AD 307), the reduction in numismatic weight from 9.7–10.5 g to a range of 6–7.9 g became significant (Figure4). • Group III began to be issued in the autumn of AD 307 and lasts until spring of AD 309, with 19 coins analyzed from three different issues (iiii). At this time the weight had been further reduced to around 6.9 g in the first two issues and 6.25 g in issue iii (Figure5). 2.3 | Experimental SetUp Xray Fluorescence was employed for the analysis of coins. FischerScope XRay XUV 773 XRF device at the Centro de Investigación, Tecnología e Innovación of Universidad de Sevilla (CITIUS) was employed; it is equipped with an Xray tube with a molybdenum anode and silicon drift detectors (SDD) with a resolution of about 140 eV. The experiments were performed at a voltage of 50 kV, a current of 500 μA, 1 mm beam size, and a 500 μm thick Al filter. WinFTM software was used to perform the quantitative analysis of the coins [2]. XRF is a surface analysis technique, with an analytical depth of approximately 45 μm in these samples. In a previous work [2], the thickness of the inhomogeneous silver layer was estimated at about 2 μm, each coin was analyzed at six different points, three on each side (obverse and reverse). The spots were selected by choosing a smooth area of the coin. In addition, to reduce variability, the median value of each element was calculated and taken as the representative concentration for each coin, with the interquartile range (the distance between the first to the third quartile) assigned as the associated error. On the other hand, to determine the concentration for a group of coins, the average value and standard deviation were calculated. 2.4 | Results The results obtained from the surface measurements of the coins show a quaternary metallic composition, with copper, tin, FIGURE 4 | Nummus of Constantius I, Divus Augustus, mint of Lugdunum, AD 306–spring of AD 307 (9.94 g; 28.07 mm) (RIC VI, Lugdunum, 202). Tomares Hoard, MASE DJ2016/0600876; ID 876). [Colour figure can be viewed at wileyonlinelibrary.com] FIGURE 5 | Nummus of Constantinus I, Augustus, mint of Lugdunum, Autumn of AD 307 (6.9 g; 30.02 mm) (RIC VI, Lugdunum, 255). Tomares Hoard, MASE DJ2016/0600702; ID 702). [Colour figure can be viewed at wileyonlinelibrary.com] 10974539, 0, Downloaded from https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/xrs.3502 by Readcube (Labtiva Inc.), Wiley Online Library on [11/07/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 6 of 10 XRay Spectrometry, 2025 silver, and lead. The alloy also shows traces of iron and nickel in all the coins analyzed, antimony in 207 of them, zinc in 165, and arsenic in only 45 pieces. Table2 shows the average composition of the sample of Lyon. The composition of the alloy used in the coins did not remain the same throughout the life of the Lyon mint. While the copper and lead content was more or less constant, there was a substantial variation, especially in the silver content. On the basis of Figure6, it is possible to identify several chronological groups, comprising several different issues, which do not specifically fall within the chronological groups established above according to the RIC VI reference, but are close to them. • The first period runs from AD 295–299, which covers part of the First Tetrarchy and corresponds to issues ivii of Group I according to RIC VI (see Table1). With a copper content of between 86.6 and 92.9 wt%, the examples of this chronology have the highest silver concentration of the entire Lyonnais series (6.1–3.5 wt%). They also have a tin content of 0.79– 2.80 wt% (although the only piece analyzed from issue viia shows 5.3 wt%). Remarkable is the presence of arsenic in the range of 0.15–0.20 wt%, which, as we shall see, only appears in some later issues up to about AD 303, after which it practically disappears. In contrast with the following group, no traces of zinc were found. • From AD 300, during the last five years of the First Tetrarchy (Group I, issues viiix) and continuing into the Second and Third Tetrarchy until around the spring of AD 307 (Group II, iiv), the silver content diminished significantly, ranging from 2.76 to 2.0 wt%. Tin, on the other hand, increased to between 4.2 and 5.2 wt% (although the only specimen analyzed of the issue viii has 1.50 wt% Sn and an Ag content of 2.67 wt%). Contrary to the previous period, from this date we begin to find traces of zinc (between 0.30 and 0.53 wt%). On the other hand, only issue ix shows traces of arsenic 0.19 wt% (22 out of 94 pieces analyzed). • From the spring of AD 307, the tetrarchic system began to show significant fragmentation, and especially in the summer of that year, the reduction of silver became more evident (Group II, vvii and Group III, iiii). Ag shows proportions below 2 wt% (with the exception of the only two pieces analyzed from issue i of Group III, with an average of 3.3 wt%). In addition, Sn reaches almost 6 wt% in some issues, while arsenic levels are undetectable in the pieces analyzed from these. Also, from this point onwards, there is a noticeable reduction in the weight of the coins in the Group III issues. 3 | Discussion As mentioned above, several authors have carried out analyses of the Tetrarchy coins struck at the Lugdunum mint using various techniques, such as neutron activation analysis, gravimetric analysis, and Xray fluorescence, among others. The general consensus is that the composition of the Lyon mint coins is quaternary; although, as has been shown, the proportions of the various elements vary from one issue to another. Table3 gives a summary of these works, with particular emphasis on the chronologies based on the issues analyzed by the various authors. The last column is reserved for the works carried out within the framework of our project. As can be seen, the sample analyzed here, which includes practically all the issues of Lugdunum from AD 295 until the spring of AD 309, is considerable in comparison with the others and significantly extends the analytical results on the metallic composition of the Gallic mint. The ix issue of group I (always from RIC VI) with 94 specimens analyzed, and the x issue of the same group with 17 examples, are noteworthy. The sample of Group II is also remarkable, as is issue i (22 specimens), which coincides with the beginning of the rule of the new tetrarchs, Constantius Chlorus and Galerius, as Augusti, and Severus and Maximinus Daia as Caesars. Our contribution is significant with respect to issues i and iii (2 and 6 specimens, respectively) of the third group (III), for which no previous analytical results were available. Figure 7 shows the contribution of these issues from the RIC VI reference work. On the other hand, Figure8 present the quantities of the main alloying elements of the Lugdunum nummi from the Tomares Hoard (Cu, Ag, Sn and Pb), with reference to the RIC VI groups FIGURE 6 | Majority element concentrations (where only one coin is in any group, the standard deviation is not shown). [Colour figure can be viewed at wileyonlinelibrary.com] TABLE 2 | Average of the concentrations and standard deviation of de coins from Lugdunum. Cu Ag Sn Pb Fe Ni Zn As Sb wt% 89.4 2.7 4.4 2.7 0.27 0.041 0.37 0.18 0.080 Standard deviation 1.7 1.0 1.4 1.0 0.17 0.006 0.17 0.04 0.025 10974539, 0, Downloaded from https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/xrs.3502 by Readcube (Labtiva Inc.), Wiley Online Library on [11/07/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 7 of 10 and issues, together with the data obtained from the analyses carried out by other authors. Despite the different techniques used, it is interesting to highlight the trend of these trace elements. As already mentioned, the quaternary composition of the coins seems clear from all the analyses carried out, irrespective of the technique used (Table3). However, it is possible to draw some conclusions from Figure8: • The content of copper is high throughout the production of the mint, although while in the first issues it remains between 92 and 95 wt%, from ad 296 there is a noticeable decrease that varies throughout the production of the different groups, with the copper content varying between 85 and 93 wt%. • As far as silver is concerned, it is evident that its concentration decreases throughout the period, as Cope [15, 16] or Bastien [9] have already noted. These authors suggested that this reduction could have taken place from AD 299 onwards, although the only coin of this chronology (Group I, issue vii) analyzed by us shows an Ag content 4.35 wt%. The greater number of examples analyzed from issues ix and x would show that it was at this time that the shortage of Ag began to be felt, with a decrease of 2.66 wt%. According to the results, from AD 300 onwards, there seems to be a progressive reduction in the silver content between 1 and 3 wt% In the following years, the reduction in weight also begins, which, as mentioned above, can be observed from the spring of AD 307, and which can be seen in the aforementioned series of Group III (with the exception of one specimen from this group, issue i, which we mentioned above). • In addition, the amount of tin increased during the life of this mint from AD 299 onwards (Group I, issue vii), coinciding with the progressive decrease in silver content and TABLE 3 | Seriation of samples analyzed by other authors and our team. Period Ref. RIC VI N° specimens analyzed Group Issues CopeaBastienbBollardcHuntdTomares teamd 294 Ii1 295 Iii 1 3 1 5 295–296 Iiii 1 1 296 Iiv 2 297 Iva 1 298 Ivia 111 298 Ivib 1 2 9 299 Iviia 1 300 Iviii 1 301–303 Iix 1 1 94 303–305 Ix517 305–307 II i22 305–307 II ii 3 306–spring 307 II iii 3 Spring 307 II iv 2 1 1 15 Summer 307 II v1 Summer 307 II vi 1 Late summer 307 II vii 122 Autum 307 III i2 Autum 307–summer 308 III ii 2 1 1 11 Autum 308–spring 309 III iii 6 309–310 III iv 1 Total 14 9 2 4 227 aGrav. chemical analysis. bChemical analysis. cNeutron activation analysis. dXRS. 10974539, 0, Downloaded from https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/xrs.3502 by Readcube (Labtiva Inc.), Wiley Online Library on [11/07/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 8 of 10 XRay Spectrometry, 2025 some changes in the design of the type. Among these is now the inclusion of the altar in the left of the field next to the Genius of the reverses (Figure9), a divinity who no longer appears exclusively naked and is occasionally shown with a hymation from Constantius Chlorus onwards (Figure5) [9]. In the coins from the Tomares Hoard, the amounts of Pb range between 2.5 and 4.3 wt%, except for the only coin of Group I, issue viii, which decreases to 1.2 wt%, while the results of Bastien and Cope show that in most of the specimens the values of this element vary between 5 and 9 wt%. It should be noted that lead segregates are usually produced [19–21]. As mentioned above, a few years ago we had the opportunity to analyze an important group of 533 specimens from the Carthage mint of the same Tomares Hoard [2]. The composition of the measurements made showed an average of Cu and Pb content very similar to that observed in the Lyon sample (Figure10). A slightly lower average silver content is observed in the coins from Lyon compared to those from Carthage; FIGURE 8 | Graphs of the alloy elements of the coins (Cu, Ag, Pb, Sn) with results from the samples provided by Cope, Bastien, Bollard and Barrandon, and Hunt) and the sample from the Tomares Hoard (where only one coin is in any group, the standard deviation is not shown). [Colour figure can be viewed at wileyonlinelibrary.com] FIGURE 7 | Number of specimens analyzed by the Tomares team and by other authors, according to the RIC VI. [Colour figure can be viewed at wileyonlinelibrary.com] 10974539, 0, Downloaded from https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/xrs.3502 by Readcube (Labtiva Inc.), Wiley Online Library on [11/07/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 9 of 10 however, due to the margin of error, we cannot assert that a significant difference exists. 4 | Conclusions This work has characterized a large group of coins struck at the Lyon mint belonging to the Tomares Hoard (Seville). The chemical composition of 227 specimens has been determined by the Xray fluorescence technique, significantly increasing the repertoire of coins analyzed from this mint for issues between AD 295 and AD 309. The contribution of the First Tetrarchy (AD 294–305) (Group I) is particularly remarkable because, although coins from AD 294 have not been documented in the Tomares Hoard, it represents an increase of more than a hundred pieces for the rest of the period (from 19 to 141 analyzed specimens). The sample from issue vii of Group I is particularly significant (94 pieces). However, the contribution of the following period (Group II) is also very noteworthy, especially with the 28 coins from issues iiii, for which no analyses were available until now. The analyses carried out in this work confirm that the coins of the Lyon mint were made of a quaternary alloy of copper, silver, lead, and tin. • The main element is copper, which remained high throughout the production of the coins, between 86 and 95 wt% in the early years. However, a gradual decline was observed from AD 296 onwards, with values varying between 85 and 93 wt% in the later issues. • The silver concentration showed a decreasing trend over time. In the earliest issues (AD 295–299) the silver content was relatively high, reaching up to 6.1 wt%. From ad 300, the content of Ag began to reduce significantly, reaching levels of less than 2 wt% in some cases by AD 307. At the same time, the weight of the pieces decreased substantially, from approximately 9.7–10.5 g at the beginning of the mint's production to an average of 6.0–7.9 g. • Although the lead content remained more or less constant, it was observed that in the coins from the Tomares Hoard the lead concentration varied between 2.5 and 4.3 wt%, with some exceptions in specific coins which had lower values. • The tin concentration also varies, since while in the first issues the tin content was relatively low, from AD 299 onwards an increase was observed, reaching values between 4.2 and 5.2 wt%. As expected, its behavior is inversely proportional to that of silver. • Traces of elements such as zinc, arsenic, iron, and nickel were also found in some of the coins. In particular, zinc did not become part of the alloy until AD 301–303, at the same time when the tin content increased from 0.30 to 0.52 wt%. Additionally, arsenic was found in the oldest issues up to the same period. • On the other hand, the composition of the coins struck at Lugdunum and Carthage is similar for four elements. • Finally, while it has been observed that Zn appears in the Lyon alloy from AD 301 to AD 303, in Carthage it appears a little earlier, from AD 298 to AD 299. FIGURE 9 | Nummus of Maximian Herculeus, Augustus, mint of Lugdunum, AD 299, (10.71 g; 29 mm) (RIC VI, Lugdunum, 59A). Tomares Hoard, MASE DJ2016/0602419; ID 2419). [Colour figure can be viewed at wileyonlinelibrary.com] FIGURE 10 | Comparison of the average composition of the coins analyzed from the mints of Lugdunum (227 coins) and Carthage (533 coins) from the Tomares Hoard. [Colour figure can be viewed at wileyonlinelibrary.com] 10974539, 0, Downloaded from https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/xrs.3502 by Readcube (Labtiva Inc.), Wiley Online Library on [11/07/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License