Unknown Rimmed Rifle Cartridge

I have one cartridge in my collection that I’m unable to identify.

(Second from left in between a .30-06 and a .45-70 Govt)

Bullet is 0.430" in diameter, casing is 2.212" long. No visible markings.

Looks to be a US-made (UMC?) .43 Spanish round.

Maybe its a 11,15x60 Mauser.

Welcome here Derringer.
The case head does not fit a Mauser which used it’s own design called “Mauserboden”. The one here has a Berdan design.

Welcome Skuldren & derringer41
As jonnyc states it is a .43 Spanish most likely of UMC manufacture, definitely not a Mauser, which has a much longer neck & not a Spanish of United States Cartridge Co. or Winchester manufacture.

It’s probably worth noting that the Spanish-produced 43 Spanish Remington cartridges originally followed the original UMC pattern very closely. They can, however, usually be distinguished from the UMC version by the fact the Spanish rounds characteristically have a headstamp, usually raised. Jack

This is a Cuban .43 Spanish with the raised headstamp Jack refers to.