A friend picked up this very poor condition Rem. RB and asked me to ID it for him. Here is a pick of the rifle and the markings on top of the barrel at the breech. I stuck a caliper in the muzzle and the bore is about .459 or so.

This appears to be the original configuration. Anybody have a clue what this is?

With those markings and that condition, my guess would be Egyptian.

Other markings? Remington two or three line on upper tang?

It has the early bar extractor and a shotgun butt, which is unusual on a carbine. The long eared hammer does look Egyptian or south American. Would guess built by Liege makers, but they usually cover it in proof marks. Might look under the forearm, if possible, for more proofs.

Cartridge identification... chamber cast is the way to go. Jillions of these were made in the late 1800s for use all over the world. Bore dimensional tolerances were all over the map, which does not help when trying to pin down the cartridge.

It looks to be a typical RB carbine, except for the buttstock. It once had a saddle ring and it looks like somebody added a buttstock from a rifle (with sling swivel) and added the extra forend band with a swivel.

My 43 Spanish has a groove of 439. 459 sounds like a sloppy 45/70...but a chamber cast would be your best bet. What works for me (I'm no professional) wad up some TP and put down in the bore beyond the chamber. Coat everything above that with olive oil. Pour hot wax down in there....let it cool for at least an hour. Gently tap it out with a good sized bore rod that has large end on it.