A C- or CE-Grade would have Damascus barrels. A CO- or CEO-Grade would have Ordnance Steel barrels. When the Model 1894 was introduced, they all had Damascus barrels. When Remington introduced their Remington and Ordnance Steel barrels in 1897, the written grade designations got an appended R or O. Apparently with the Model 1900s the Remington Steel barrels were considered standard and the grade designations were K- or KE-Grade and if a Model 1900 had Damascus barrels a D was appended to the grade designation -- KD- or KED-Grade.
What you are reading as an F in the serial number on the trigger guard tang is really a P, the Remington Arms Co. inventory letter for Model 1894 doubles. The letter for the Model 1900 doubles is Q.
