Given the roller spring and the flat slabbed shape of the comb on the cock I would guess British, probably later i.e. post Rev War rather than earlier - very possibly early 19th century. There have likely been some corrosion losses to the plate - it may not have been rounded at the tail completely, there may have been a smaller tit that has simply rusted away. Also while there is no internal bridle now, there looks to be a shadow of an internal tumbler tit or shaft, so possibly it had an internal bridle originally and at some point was 'repaired' or adjusted crudely?