Assm line pumps & very early NOS pumps will have a 2 letter code. The 1st letter is the month A-L indicating A=January etc. The 2nd letter indicates the year F=1966, G=1967, H=1968, I=1969, & J=1970. In 1971 pumps had Julian dates 1-365 followed by a letter. K=1971, L-1972, etc. A 123k40727 would be May 3rd 1971....Joe