the Westley Richards website puts Ser. No. a3911 as being built between 2016 and 2026. So I took the "a" off and it shows Ser. No. 3911 as being built between 1825 and 1835. I've seen WR "crab knuckle" hammer guns that were supposed to fire either pinafore or centerfire cartridges, but I don't know the truth of that.