Is there an inscription on the rib? A Pieper gun could have have Belgian proofs if sold there. The gun has English proofs and no Belgian as far as I can see. Some countries allowed export without proof as long as they were exported from the factory. They would then be proofed at the destination. The gun looks to be a higher grade than the normal Belgian contract gun.
You might want to post at
https://www.doublegunshop.com/forums
There is a lot more interest there in European guns. Some overlap with here, but there is not a lot of interest here in "not Parkers".
By the way, those are not back action locks. They are the later type. Probably made in 1880-1900 is my guess.