TRACKSGUNSMIHING,
Records show that in the city of Barnstaple, U.K. there was at at some date date a gunsmith/dealer or ironmonger[hadware store] that traded under the name Mortimer.Examples of cartridges marked "Mortimer,Barnstaple,The Club,"exist.Could this be the mysterious R.S.Mortimer? Or is this is just another Belgian gun bearing a spurious name?
Perhaps barrel browner [At one time a frequent poster on this forum who resides in Barnstaple] could help because I am aware that he is working on a reference book related to the gunmakers/smiths that have carried out business in Barnstaple in the past?