21 mm diameter, 3.23 grams (50 grains), plain edge
1927,1935,1937,1939,1940,1941 Bronze alloy (95.5% copper, 3% tin, and 1.5% zinc)
1942,1943,1944 War time bronze alloy (97% copper, 2.5% zinc, and 0.5% tin)
1946,1947 Bronze alloy (95.5% copper, 3% tin, and 1.5% zinc)