Vintage solid gold COIN 8K miniature in brass frame Pope Joannes XXIII special

Vintage solid gold COIN 8K miniature in brass frame Pope Joannes XXIII special. Diameter of the coin: 0.3 inch / 1.1 cm. Measures of the frame: 1.8:x 2.8 inches. The world's smallest gold coin.

8k gold could tarnish from sulfur and ammonia in the atmosphere. Copper, in particular, likes to react with oxygen (moisture) and this can lead to discoloration or tarnishing greenish to brownish. The coin is over 40 years old.

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