Hello Kingman60, you got my attention, I have some four digit mod 39s
with what is referred to as the military mag. The sides are cut out to reveal the cartridge count. the follower should be in the shape of an eight(8) or X and the base plate stamped S&W. They were first available on the parts list in Sept. of 1958. Pls. post the Sn. or send me a PM. OH! and the matching numbered blue box. Very nice. Good snag. best, Mike

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Mike 2796
SoFo Bunch member