3836848 - 1956-1962

GM21 = ? (where on the head)

CON9 = conveyor #9

J 12 1 - date casting code
J = month = 10 = October
12 = day = 12th
1 = year = 1961

http://www.1954advance-design.com/Web%20images/casting-code-photos/codes-ser-nums.html