20 Zlotys Jan Długosz

Jan Długosz (1415–1480) was the medieval chronicler whose twelve-volume Annales seu Cronicae incliti Regni Poloniae remains a foundational source for Polish medieval history — and the reason his image appears on a commemorative issue rather than a circulation note. This 2015 piece is one of Heidrich's later commissions; he designed the vast majority of Polish banknotes from the 1960s onward, making his credit here on both the design and obverse engraving something of a final-generation signature on a series he largely defined.

The security specification is minimal by modern standards — watermark and thread only, consistent with a collector-oriented release rather than a note intended for heavy use.