Can someone please help me with the type and value oF this pistol? The only markings on it are on top of the barrel and say "CONSTRUCTED FOR ,MESSRS GYE & MONCRIEFF LONDON." The wooden grips are about 90% with very few scratches. There looks to have ben a lanyard clip on the butt at one time. The barrel, cylinder and hammer have better bluing on them than the rest of the pistol.