Władysław II Jagiełło Grosz

The most intriguing fact about Władysław II Jagiełło's grosz is that it helped unify Poland's currency system shortly after his 1386 marriage to Jadwiga, blending Polish and Lithuanian influences into a single silver denomination. This coin, roughly the size of a modern thumbnail, was struck to facilitate trade across a patchwork of regions.

Minted from locally sourced silver, likely from the mines in southern Poland, the grosz featured a simple cross on the obverse and the king's monogram on the reverse. Variations exist, but records of exact designs and mintages burned in an 18th-century fire, so we're left with fragments. I've turned a few over in my hands; they're heavier than you'd expect for their age.

One dry note: Some call it the "poor man's ducat," but that's generous—it's more like the accountant's choice for balancing ledgers.