I have recently obtained an sxs 32" hammered, dual trigger L C Smith. The serial number search reveals it to be manufactured in 1917. There is an "F" stamped below the serial number, does this stand for field grade? No where on the barrels or frame does in designate the calibre, where do i find that marking? I have removed the barrels and looked everywhere on the frame and barrels. Did find they are Royal Steel.