The F at the end of the serial number is for Folsom, H & D Folsom Arms Co. in NYC that acquired the Gun portion of Baker Gun & Forging Co. about 1919. Folsom continued to make/assemble Baker guns, most likely at their Crescent Fire Arms Co. factory in Norwich, Conn., to about 1929. Whether the chamber is 2 5/8 or 2 3/4 inch to the break from the end of the chamber to the forcing cone, it was intended for 2 3/4 inch shells.