Unlisted in Janusz Parchimowicz's"Polish Proof Coins 1949-1990" catalog, a technological sample of a twenty-zlotycoin minted for the XXX anniversary of thePolish People's Republic (Miner, Metallurgist, Farmer and Soldier types).
Obverse stamped with the stamp used for issuing nickel trials, with the characteristically crooked inscription PRÓBA (to the left of the outline). With the monogram WK at the bottom.
Reverse known from the sample minted in 1 piece (sic!), without the mint mark under the eagle's paw (as item P.299.c).
Mint, with mirror and patina.
Copper-nickel, diameter 29 mm, weight 10.21 g.
