Certainly not impossible, I couldn't comment on what S.R. would mean, but I do know not everyone had their lanterns stamped at the factory I have one streamlined Blizzard and one Little Giant dated 1941 that were taken home from the North American Aviation plant in Inglewood, California by an employee when they were no longer of any use, N.A.A. just added an extra heavy coat of red paint and simply stenciled N.A.A. on the bottoms of the tank. I keep them just as they are un-restored because they remind me of the day when my father, who also worked for North American, took me to the plant as a boy to show me several P-51 Mustang fighters they had lined up in the lot. These lanterns saw service there probably on barricades during the same time the P-51s were being manufactured.
W.M.