Barrel lenth of a 7.65 DWM cAlphabe Commercial

[alicat]

A plumber found this during Prohibition behind a toilet in an apartment in Saint Paul where Chicago gangs went when it got too hot IN Chicago. He gave it to my Dad and I inherited it in 1954. Dad never fired it and I only began firing it a couple of years ago, perhaps 200 rounds. It is 7.65, GESICHERT, DWM, 1303 n, GERMANY on left rail, Cr N on barrel and frame, all parts match except magazines. Buttstock lug, no grip safety. Mechanically perfect, no pitting inside or outside, 98% original blue, wood grips are clean but very dark brown. Curiously, it has a 3.75" barrel which I haven't seen on any Alphabet Commercial 7.65. Comments?