20 mm diameter, 2.91 grams (45 grains), plain edge with center hole
1927, 1934, 1935, 1939, 1941 Cupronickel alloy (75% copper and 25% nickel)
1942, 1944 Bronze alloy (97% copper, 2.5% zinc, and 0.5% tin)
1946, 1947 Cupronickel alloy (75% copper and 25% nickel)