Mystery ammo 1: Scalloped headstamp on rimless 7.5mm cartridges. I don’t see the B P or SMI headstamp in the IAA list, but I realize that is only a first check. The bullet diam = 7.55mm, case length = 51.15mm +/- 0.05mm.
This is the first of about five types of misc cartridges I found in a full shoebox of ammo I got as part of a purchase of cast lead bullets for .44 and .45. Didn’t really want them, but seller threw them in to get them off his hands. I am asking here for assistance in identifying cases to make sure I don’t just strip and recycle a cartridge someone could use in their collection. Most are pretty straight forward as being 6.5mm variants from WWI era, but a few I’m having trouble identifying. Photos attached. Thank you for any help you can provide. Photo added to better show scalloped case heads.