Crown over “BNP”
Birmingham commercial proof house since 1954 - definitive nitro proof
.38, .767”, 3-½ Tons
Caliber, case length and proof pressure
Crossed swords H3B
Birmingham date code
H= 1957 (Inspector 3)
http://www.hallowellco.com/proof_date_codes.htm
The British love to stamp the snot out of guns. Never loan them one!