Czy informacje zawarte w stemplach monet są w pełni wiarygodne?

It is widely believed that the data contained in coin designs are fully reliable. In fact, the metrical data, i.e. information about the issuer, place and time of mintage are not always accurate. This can be the case of modern or even almost contemporary coins. Dates on coins happened not to be updated under Russian partition, German occupations during the WW II and Russian occupation in Polish People Republic. Unmatched record are thalers with an image and name of the Empress Maria Theresa (d. 1780) minted in large quantities in different countries with the same design for two hundred years. Although a similar situation could have existed in the early Middle Ages, we are lacking written sources to confirm that. The very coins are thus the only source. There are two main reasons why designs, these certificates of coins, happened to be false: first, because foreign coin designs were imitated; second, because own coin designs were not changed and thus underwent immobilization. In the first case, coins with the best reputation were imitated: Roman, Byzantine, Anglo-Saxon and Cologne coins, but also gold Arabic dinars. The best known examples of immobilized coins are Carolingian and Saxon pennies and pfennings with the names of the King Otto III and the Empress Adelheid. The latter were minted in large quantities for more than half a century. Therefore they were imitated both in Saxony and Poland, where also Anglo-Saxon, Bavarian and Czech patterns were copied. The best way to identify the real issuer, place and time of issuing of various imitations is to examine the die-links between these imitations and coins with ascertained designs. Nevertheless, sometimes new information contained in the designs of coins, and not taken from outside or from the past, is false. Good example are the twelfth / thirteenth century regional issues of a number of dukes in Poland who did not possess the right of minting. Therefore they issued coins with the names and images of their late fathers or even earlier ancestor. Errors in identifying coins may, however, arise not only from entrusting the false certificates, but also because of the improper interpretation of the designs. It is assumed, for example, that the legends explain the images from the field. In fact, words and images were separate elements that did not have to match. Falsifying legends occurred more frequently than one might expect in different times and on various territories. The driving force behind such actions was mainly economic, and sometimes also political. Accidents also played role. Therefore one must first thoroughly examine a coin, before he makes an attempt to interpret it as a historical source. Slightly extended version of this text in Polish was to appear in the publication of materials from the conference Money and Banking in Great Poland held in Poznań on 20-21 November 2008 (35 figures)