Here's the decoder for the date stamps:
There should be two capital letters within a square box; these are date stamps and can be used to determine when the gun was made. AA means 1975, AB is 1976, etc. AG, AJ, AK, AO, AQ, AR, AW and AV are not used, so AZ is 1990. BA is 1991 and BE, BG, BJ, BK, BO, BQ, and BR are not used so BT is 2003. My list stops there, but I presume that BU is 2004, BZ is 2005 and CA is 2006.
Before 1975 Roman numerals were used: X for 1954, XI for 1955, etc. through XXVI for 1970. Then XX7 was 1971, XX8 for 1972, XX9 for 1973 and finally XXX for 1974.