My Grandfather was in WWI and it was said that this was his service revolver. He was also a local policeman and chief in the 50's. The serial number on the butt is obscured and the strap ring has been filed off. The serial number on the cylinder is also obscured. The serial number on the under side of barrel is the only markings still legible. They have letters in front, B-F 27803. The low number should mean manufactured in 1918. But what is the B-F? How can I find origins of this gun? Perhaps it was taken during his police service. Any help is appreciated.