Mine was the M52-1, the –1 signifying a modification of the original M52’s trigger system. Original M52s had the double-action trigger system of the M39 with a lockout screw installed to fix it as a single-action, but competitive shooters found this unsatisfactory. In May of 1963, the M52-1 was released with a redesigned, solely single-action trigger system. In 1971, the M52 was again further improved when its extractor system was changed from a spring bar type (that was prone to occasional breakage) to a narrower assembly powered by a coil spring. This third and final gun was designated the M52-2, and it remained in production until 1993, when due to lagging sales, it was dropped from the S&W line.