The J 3 stamped on the hub refers to the year and month of manufacture starting from 1931 . The letter is the year, the number is the month;
- A would be 1931
- B = 1932
- C = 1933
- D = 1934
- E = 1935
- F = 1936
- G = 1937
- H = 1938
- I = 1939
- J = 1940
- K = 1941
- L = 1942
- M = 1943
- N = 1944
- O = 1945
- P = 1946
- Q = 1947
- R = 1948
- S = 1949
- T= 1950
