Perrin, your gun dates to 1919, shortly after this date the push button release (Curtis Forend) was replaced. A shame because a lot of Field Grade non-ejector forends were lost because of the change. On other grades they used surplus roller release forends on non ejector guns. The FW refers to your gun as a Featherweight. Differences are the number of screws holding the sideplates on, the shape and size of the sideplates and the size of the barrel lug that protrudes through the bottom of the receiver. I don't know what the "C" is referring to. On this year it is to early to have proof marks stamped on the barrel flats.