An early 19th century English flintlock pistol of unusually large bore

An early 19th century English flintlock pistol of unusually large bore, octagonal twist barrel 6 in., top flat marked 'COLLINS LONDON', approximately 10 bore, hooked breech, engraved tang; engraved lock marked 'COLLIINS' and with safety bolt and roller bearing to the frizzen spring; walnut stock with engraved steel trigger guard, captive ram rod.