TheAntiqueTrade.co.uk Glossary of Antique Terms G
Gun-makers Marks - (Weapons) The testing of barrels to ensure a standard of safety, 'proof-firing', was entrusted to the Gunmakers' Company of London in 1637. There are two kinds of small proof mark, both headed by a crown. The letter 'v' on the first mark means 'viewed after the first test'; the letters 'Gr' on the second mark stand for 'Gun-makers' Proof'.
The Official Guide to Gunmarks: Third Edition