One more thing:

The rifle cartridge marks were pointed out to be : "172.28" and "58".

172.28 is a bore size that converts to .300 in caliber and 8mm in metric. If 58 is a length of 58mm that would be a case length of approximately 1.4732". I have to make a chamber cast when my cerrocoat gets here, but I believe this is a straight cartridge with a rim.

Can anyone guess what type of cartridge might have existed in Germany around 1911 that was 58mm long with an 8mm or .300 bore that was straight walled?