1877 Twenty-Cent Piece. Proof-61 (PCGS).This fully struck, lightly toned example is awash in smoky silver gray iridescence. Ample reflectivity shines forth from the fields as the coin dips into a light. With a mere 510 coins produced, all in Proof format, the 1877 is the lowest mintage and scarcest date in the brief twenty-cent series of 1875 to 1878.