1899Cs weren't cataloged after WW1. The octagon and 1/2R 1/2O barrel configurations, along with the 25-35, 32-40, and 38-55 chamberings weren't cataloged after WW1. If you have a receiver with a post-WW1 serial number and any of the 5 attributes that I have noted, it is (probably) either an original gun made from leftover pre-WW1 parts or it isn't original. Also, I believe that the "standard" cataloged octagon barrel length was 26", so a 24" octagon barrel would seem to be either a special order or cut.
Jeff
