100 Zlotys Casimir III the Great

Casimir III — the only Polish king history awarded the epithet "Great" — died in 1370 after a hunting accident, leaving no legitimate male heir and ending the Piast dynasty after over four centuries. His reign transformed Poland's legal and administrative infrastructure so fundamentally that contemporaries said he "found a Poland of wood and left one of stone." This issue was struck as part of NBP's long-running royal portrait series, which began in the 1980s and has systematically worked through the Polish monarchy.

The .900 fine gold specification places it outside standard bullion parameters — clearly a collector issue from the outset, with no pretense of circulation.