??? This one is strange. The cartouche letters are David Francis Clark, but this version cartouche was used on SAA Colts much later about 1885 time frame. The Remington-Lee as Richard noted above was a entirely different version of his cartouche. Letters had periods after each and shape of outline was a rectangle with corners cut off in 1883 time frame. He had six versions of his cartouche. "U.S. Military Arms Inspector Marks" by Charles Pate does not list him for the Remington Split Breech Carbine. The inspector most commonly found on the Remington Split Breech is Charles Graves Curtis, but this carbine shown is not his mark.