U.S. Coins Three-Cent Nickel Minted: 1865–1889 Diameter: 18mm Composition: 75% copper, 25% nickel. Gold $2.50 Quarter Eagle (Liberty Head & Indian Head) Minted: 1840–1929 Diameter: 18mm Composition: 90% gold. Foreign Coins Mexican Gold 5 Pesos Diameter: 18mm Composition: 90% gold. Swiss 20 Rappen Diameter: 18mm Composition: Copper-nickel. Austrian 20 Heller Diameter: 18mm Composition: Zinc or other alloys (varies by year). Japanese 1 Sen (Meiji Era) Diameter: Approximately 18mm Composition: Bronze. French 10 Centimes (Napoleon III) Diameter: Around 18mm Composition: Bronze or copper. British 1/5 Sovereign Diameter: Approximately 18mm Composition: 22K gold. Bullion Coins 1/10 oz Gold Bullion Coins Examples: American Gold Eagle (1/10 oz): 16.5mm (fits loosely in an 18mm holder). Canadian Gold Maple Leaf (1/10 oz): 17mm, but may fit 18mm holders snugly. Mexican Gold Libertad (1/10 oz): Fits 18mm holders well. Private Mint Rounds Many fractional gold or silver bullion rounds measure around 18mm. Summary Coins with an 18mm diameter include: U.S. Coins: Three-Cent Nickel and $2.50 Quarter Eagle Gold. Foreign Coins: Mexican Gold 5 Pesos, Swiss 20 Rappen, Japanese 1 Sen, and others. Modern Bullion: Fractional coins like the 1/10 oz Gold Maple Leaf and American Gold Eagle.
