Definately english, maybe a "real" Manton, hard to tell. "Real Mantons" tend to be fairly high end, the lower end guns many times made in Birmingham with Mantons name engraved and sold out of Manton's shop.
I think you need to separate the original John and James Manton from the later John Manton which tended to be economy guns (better than belgian) which were a continuation of the family name under John's widow and the shop foreman. Unless I am mistaken they carried on into the cartridge era.
Also re W Richards; keep in mind there was also a William Richards who made economy grade guns and was english. Final note is that an unproven gun shipped to and sold in England would have been given an english proof before sale. The english proof mark was therefore not necessarily a forgery done in Belgium
cheers Doug
You meant to say "the original John and
Joseph Manton".