Watch List notes:

Nicholas I (1825-1855), Proof 20-Kopeks, 1855-CNB, Nicholai Iossa, crowned double-headed eagle, rev. crowned value and date in wreath, incuse edge graining, 12h (Sev. 3628; Uzd. 1723; Diakov 668; Bitkin 346), streaky tone, otherwise brilliant much as struck, in NGC holder, graded PF63 (Cert. 3074765-001)

provenance
Stack's (New York), 10 January 2011, lot 908