.22LR - .45ACP Colt Conversion Unit for M1911 & Government Model

Year Approximate Serial Number
1938 U1
1939 U400
1940 U900
1941 U1100
1942 U1400
1943 U1701-U1750
1946 U2001-U2670*

*Colt Conversion Unit's continued to be produced past this time but this is the last recorded serial numbered unit.

 

.45ACP - .22LR Colt Conversion Unit for the Service Model Ace

Year Approximate Serial Number
1938 U1
1939 U18
1940 U61
1941 U112