SaxonPig, my non-RM is a very late shipment to KCPD, July of 1940, and does not have the Registration number. Actually, there were less non-RM's made than RM's (1400 vs. 5224). Mine is one of very few that has not been refinished, though it does show some wear. My magna grips number to the gun, also.
(Above production figures from Nahas and Supica's SCSW, 3d. Ed.)