Interesting, thank you. I've looked through some online databases of yataghan bayonets, and it looks like Remington ones have unchamfered hilt slots. Mine's chamfered, which make me assume it was for a chassepot.
Old smithy's database mentions a Remington bayonet "marked with Alex Coppel balance on left side of blade and has a "C" in a circle on the right hand side. Has un chamfered hilt slot" That's close to mine except mine has a "B" instead of a "C" and the hilt slot on mine is chamfered.