Iron axe-like grzywnas (also referred to as proto-currency or axe-like bars) are characteristic early medieval artefacts, the function of which has not yet been explicitly determined (e.g.: supplementary money, semi-processed raw iron prepared for transportation).
The so-called “treasure of Vistulans” was discovered in 1979 on the property at 13 Kanonicza street. The treasure amounted to 4212 grzywnas with a total weight of approx. 3630 kg.
Iron grzywnas appear in archaeological collections dating back to the period between the end of the 8th century or the beginning of the 9th century and the mid 10th century. This largest known treasure of grzywnas was hidden in the second half of the 9th century (archaeological dating confirmed by radiocarbon dating).
Lesser Poland was known for several small treasures and single findings before. In Slovakia and Moravia, about 3 thousand artefacts, in total, were discovered, with the highest concentration in the settlement centres of Great Moravia.