I’ve had these cartridges for a while but never really looked into what they are exactly. They measure 7.92x53.5 and are rimless. Their outwardly appearance says 7.92x57 Mauser but they are shorter. I see that there is a 7.65x53 “Belgian Mauser” round but this doesn’t quite match that. If you can’t make out the headstamp, it’s marked “F N” (on the 9/3 o clock position) and “S” at the 12 o clock and “34” at the 6 o clock. I’m assuming these were made in Belgium in 1934 but correct me if I’m wrong. They came in a stamped sheet metal machine gun feed strip marked “Belgian Hotchkiss” by hand but that doesn’t mean they are correct to the feed strip.