RRC is marked on all scabbards I have ever seen, so I have always thought they were a manufacturer mark; however they scabbards were made by the Hugh Carson Company from 1909 to 1917 (according to the Ross Rifle story). Later in 1942 another batch was made. As seen by your markings, it is the MkII version of scabbard, which is correct for the MkIII bayonets.