Just by chance I was looking at a Holts catalogue from September last year and came across a similar Pape gun .It had been reproofed and also claimed to have re-bounding hammers which suggests a later modification .
The provenance stated that the gun 1818 was delivered in July1870 as No1 of a pair and that the gun was supplied to Pape by the gunmaker Wilkinson .I assume that this is the Wilkinson that became Wilkinson Sword now best known for razors .