The attached cartridge case is nominally 9mm caliber, but I cannot identify it. It is possible that it is cut down from something. The head is reminiscent of the “G” Tesching cartridges but the case isn’t the right length. It is Berdan-primed but the roughness of the primer pocket bottom and anvil make me suspicious.
Case length 1.77" (44.96mm), rim diameter .45" (11.43mm), head diameter .393" (9.98mm), case mouth .383" (9.73mm), inside case mouth .355" (9.02mm). The headstamp is delightful though I have no idea what the “40” at 9 o’clock and 3 o’clock means.
Any info on what it is and/or what the headstamp means would be appreciated.