A hoard of several hundred Roman Republican denarii and their barbaric imitations, as well as some Augustus denarii came to light at the foot of Gellért Hill in Budapest in 1901. This hoard confirmed that the barbaric imitations were minted by the Eravisci who lived in this area. One of their major settlements, an oppidum was identified on Gellért Hill and smaller settlements of this tribe are also known from the surrounding area. The legends on some coins include the tribal name in the form of IRAVISCI or RAVIS. The Eravisci were the single Celtic tribe in Pannonia whose coinage was based exclusively on Roman Republican denarii and they are also the single tribe who inscribed their tribal name on their coins. This coinage, dated to the dawn of the Roman rule in Pannonia, raises several important questions. Knowing that earlier Celtic coinage was modelled on Greek types in this territory, why did the Eravisci use Roman prototypes? Why did this tribe begin to mint coins at a time when elsewhere Celtic coinage was on the decline? How and why did these Roman prototypes reach this area, especially in the light of the fact that the archaeological record does not reflect intensive trade contacts with Rome during this period. Surprisingly enough, however, a high number of Roman Republican coins have been found in the Eraviscan settlement territory. These coin finds offer invaluable information on the process of how Pannonia was occupied by the Romans. The written sources contain little information on the conquest of Pannonia. Roman historians mostly report on the events south of the Drave and along the Amber Road, but they rarely mention what happened in eastern Pannonia. It is generally accepted that eastern Pannonia was incorporated into the Roman Empire around 50 A.D., during the reign of Claudius, in other words, the organization of the province was the result of a longer process. In any case, the presence of Roman Republican coins and their imitations suggest that the Eravisci had maintained intensive contact with Rome well before the creation of the province. If these contacts were not commercial or economic in nature - and there is nothing in the archaeological record to suggest this - we can only assume a political one, such as an alliance. This would fit in with what we know about Roman foreign policy. It seems likely that the neutrality of the Eravisci was bought with these coins in order to ensure that they would not become involved in the anti-Roman revolt of the tribes living between the Drave and Save. Although this is only a hypothesis, it clearly demonstrates the importance of the numismatic material in the reconstruction of historical events.
The above example is an excellent illustration of the basic task of numismatic studies. Numismatics can be defined as the study of coin shaped objects made from metal and objects closely resembling them in form or function, such as emergency coins and various tokens used instead of money, as well as memorial medals commemorating various events, individuals or anniversaries, and various decorations, awards and badges, especially from an archaeological or historical viewpoint. Modern numismatics also includes objects that are no longer coin shaped, such as paper money, shares and bonds, as well as credit cards and phonecards. Numismatics as a discipline covers a wide area in both time and space. It is therefore obvious that research methods and the conclusions that can be drawn from the study of numismatic objects differ from period to period. The examples mentioned in the following are taken from classical numismatics, since this happens to be my own field of research. The first step, obviously, is the identification of the object, of where, when and under what circumstances it was made, who issued it and for what purpose. In most cases this identification is relatively simple since most coins were produced by the state, and in this sense they are official documents that clearly state in their legend and design which authority they were issued by. Roman Imperial coins can be dated fairly easily, sometimes to the year, on the basis of the imperial titulature, but at least to the reign of the emperors which is known from the historical sources. Some of the coins of antiquity bear a date that can only be interpreted in knowledge of other contemporary chronological system, such as the coins of Hellenistic and Roman Egypt that bear the number of the ruler's reigning years. Owing to their precise or relatively precise datability, coins are one of the most important sources for dating archaeological finds and features, even if one must consider that the date on the coin refers to the time of its issue, a fact that has little to with the length of its circulation. The definition of how long a particular coin was in circulation after its issue is a thornier problem. Coins are in themselves archaeological objects and any conclusions drawn from their study are less reliable than the information contained in written sources (although these are often also unreliable!). The interpretation of coin finds has many pitfalls. Even so, coins constitute one of the most reliable means of dating. It must also be borne in mind that the chronology of certain coin types is more problematic than of Roman ones. In the case of the coins issued by the Greek city-states, for example, one can determine fairly easily where they were minted from their legend or from the design. In contrast, the determination of their date calls for various analyses and the examination of other available sources of evidence, such as the composition of coin hoards, overstrikes, the sequence of the use of dies, the possible correlation of the designs with historical events, the find circumstances, style, etc. Another aspect of numismatics must be mentioned in this respect, namely the investigation of a mass of coins, rather than a single piece, since coins - money - were a mass product, issued in several thousand or millions of specimens. Most hoards usually contain only a few specimens of the oldest coins and the number of issues that fall closer to the date of deposition is higher. At the same time, even the 'freshest' coins are not present in large quantities in a hoard since a certain period of time had to elapse before they become part of the monetary circulation. If a hoard is predominantly made up of 'fresh' issues, we must assume a rather special case, such as the concealment of a larger amount of cash fresh from the mint or the central treasury, or the deposition of soldiers' pay or the amount of tax collected from the inhabitants.
Another aspect of numismatic studies also has a bearing on the study of ancient economies. In this case coins are not studied as individual objects, but rather as a mass product. Coins functioned as mediums of exchange and money in antiquity and in the Middle Ages, including the large medallions that, even though not made for circulation, nonetheless represented wealth owing to their precious metal contents. Being objects that can be reliably dated and reliably sourced, coins are often one of the most reliable sources for the reconstruction of economic history, especially for periods from which there is little in the way of written sources. One case in point is the reconstruction of the trade contacts based on coin finds. The types, denominations and countermarks on the coins also offer valuable information on the nature of the trade contacts between two areas. In the later 6th century B.C. the northern Greek city-states and tribes which had access to silver resources issued large sized silver coins weighing 4 and 8 drachms that occur in hoards from Egypt and the Ancient Near East, both areas that did not have a coinage of their own. The coins in these hoards did not function as money, but as raw material, and since worked metal was more valuable than raw metal, the issuers and the exporters made a rather generous profit on this trade. The Persian invasion and, later, Athens' increasing economical and political power during the 5th century B.C. put an end to this lucrative trade. Hundreds of city-states issued coins in the ancient Greek world. Although some of these coins were minted for a specific occasion and for local use only, others, such as the coins issued by Athens, were used throughout the Mediterranean world and functioned as a kind of international currency, rather like the US dollar in our own days. Their "immobile" type (permanence of the design), the helmeted head of Athena, representing the city state on the obverse and the goddess' sacred animal, the owl on the reverse, - reflects this function. These good quality coins, called "owls", preserved their value and were accepted and used for long centuries.
In the Hellenistic monarchies where the rulers often issued overvaluated coins there were strict restrictions against foreign currencies, primarily against currencies based on the Athenian standard. The Ptolemies, the Seleucids and the rulers of Pergamon only allowed these coins to enter circulation after a major devaluation as shown by the countermarks. Countermarks indicating devaluation are also known from the beginning of the Roman Empire. Nero (54-68 A.D.) did not issue new bronze coins in the first part of his reign and instead had countermarks indicating devaluation struck on the old, worn bronze coins minted by his predecessors: a dupondius mark on the highest denomination, the sestertius and an as on the dupondius.
Coins are often the only source of information on the economies of ancient states and they remain an important source of evidence if there are written sources, such as the Athenian coinage decree. The surviving fragments of this decree suggest that under Pericles Athens strove to impose a uniform system in the Delian Confederacy, to suppress non-Athenian coinage and to make Athenian coins the norm throughout the Aegean. However, the coin finds from this period clearly show that this goal was never realized.
The importance of coins from periods that are well documented in the written sources can be illustrated with another example. The account books and tax registers of the Turkish occupation period in Hungary only mention Turkish coins, the akce, while the actual coin finds from this period are predominantly made up of Hungarian and various foreign coins, rather than the akce, indicating that although the authorities made their calculations in akce, monetary transactions were conducted in other coins.
Coins are also a good source for political history. Certain rulers of the Indo-Bactrian Hellenistic kingdom are known only from the portraits and names on their coins. But even in the case of the Roman emperors, whose lives are amply documented, the study of Roman coins can contribute new data. The name of the Empress Salla Barbia Orbiana is known only from coins, and these coin finds also indicate that she was the wife of Alexander Severus (222-235).
Functioning as money, coins had a predominantly economic function, but in the Roman period they were, for example, also an important medium of propaganda by means of their legend and design. The coins not only offer information about the ascension of a new emperor - since the first act of each new emperor was the issuing of new coins bearing his portrait and name, even if he only held the throne for a couple of weeks - but also about major events, military victories, the conquest of new lands, political programmes, dynastic ambitions, the real or desired condition of the state, the introduction of new religions, events in the imperial family, either in a factual or a symbolic form. Coins, especially the bronze coins minted in the provinces for local use, also offer valuable information on daily life: for example on crafts, sports events, cults, local buildings, treaties. The latter are represented by the so-called homonoia coins, offering evidence for cultural contact between what would today be called sister cities. The coin designs are also an invaluable corpus for scholars researching social and religious history.
As artworks, coins reflect the style of their age and, being well datable finds, offer good chronological anchors for art history. Some coins bear depicitons of buildings and statues that have perished and are known only from literary sources, such as the lighthouse of Pharos and Pheidias' statue of Zeus in Olympia.
Being a corpus of primary and contemporary finds, coins are invaluable for historical research, as illustrated by the examples mentioned in the above. It is indisputable that numismatic studies can contribute much to the study the so-called archaeological periods - antiquity and the Middle Ages - and that the closer we get to the Modern Age, the importance of coin finds wanes since they offer little additional information to what we know from other sources. "This does not mean that the study of modern coinage is useless. Human attitudes towards coinage have changed surprisingly little over the centuries, and the observation and study of numismatic phenomena in a modern context, where written evidence and the comments of contemporaries are available, can sometimes suggest explanations for similar phenomena in the past."
Few phenomena in human history have been the focus of so much constant and fevered attention, occasioned so many moral and religious strictures and been the cause of so much violent strife and competition between individuals and states than the money. Thus, the study of the history of the coins and money is one of the most important tasks of historical research.
 Gohl, Ö.: A budapesti eraviszkusz éremlelet [The Eraviscan coin hoard from Budapest]. NK 1 (1902) 17-45.
 Bónis, É.: Die spätkeltische Siedlung Gellérthegy-Tabán in Budapest. Budapest 1969; Pető, M.: Neuere topographische und archäologische Angaben zum Leben der Siedlung Gellérthegy-Tabán und Umgebung in der frühen Kaiserzeit. ActaArchHung 31 (1979) 271-285; Novák, Gy. - Pető, M.: Neuere Forschungen in spätkeltischen Oppidum auf dem Gellértberg in Budapest. ActaArchHung 40 (1988) 83-99.
 Gohl, op. cit.; Torbágyi, M.: Die Münzprägung der Eravisker. ActaArchHung 36 (1984) 161-196; Fitz, J.: Die Eroberung Pannoniens. ANRW II/6 1977, 543-556.
 Tóth, E.: Megjegyzések Pannonia provincia kialakulásának kérdéséhez [....]. ArchÉrt 108 (1981), 13-30; Fitz, op. cit.
 Torbágyi, M.: Elfelejtett római éremleletek. III. rész (Im Vergessenheit geratene römische Münzfunde III. Teil). NK 96-97 (1997-1998) 14
 Grierson, Ph.: Numismatics. London-Oxford-New York 1975, p. 4.