Poland
Republic nickel Proof 20 Groszy 1923 PR66 NGC, Vienna mint, KM-Y12, Gum-2592. Delicately frosted on the motifs, with no distracting post-strike imperfections or discoloration that diminish the wonderful eye-appeal. Reportedly only struck with a minuscule mintage of only 10 proofs.
Estimate: 1500-2000 USD