It does have rebounding locks, which puts it a little later than the forend wedge might imply.

It's definitely a BPE, and I agree it's pre-1899.

There will be black powder proofs. The "V" with crown over if proofed in London and the bore marking that corresponds to .40 caliber, in all likelihood (if it has ".400EX" it's a bit later). I don't have my reference works at hand to say what year the caliber marking was mandated.

I would want a chamber cast before making any judgment about what cartridge it should have. Could be .450/.400 3.25" BPE, but could be something different also.

Curl