Unlisted in the catalog of Polish proof coins 1949-1990 by J. Parchimowicz's technological sample of a twenty-zloty coin minted for the XXX anniversary of the Polish People's Republic (Miner, Steelworker, Farmer and Soldier types).
Obverse without the mint mark under the eagle's paw (like item P.299.c), reverse similar to P.299.b, but with a different arrangement of the PRÓBA inscription.
Minted, in patina.
Mintage of up to 24 pieces (for all varieties).
