Not a super authority on continental guns but I would agree gun is number 2 of a pair. Could this be a birmingham gun built in Belguim with English tubes?? I know some of the lesser know English firms outsourced some work at one point. Gun appears to be quality. It is a sidelock with ejectors. Most of the cheap Belguim "trade" guns were boxlocks, and had extractors. This gun is of higher quality than one might think...

Double guns and English Setters