Stephan, thank you kindly for your enlightening response. I wonder what I should do with it then. I was planning on installing it on a new barrel for a parts gun I'm building but feels a bit to rare for that!This rear sight base was manufactured by "Nähmatag - Nähmaschinenteile AG" in Dresden, usually it belongs to a K98k that was assembled by the company Gustloff-Werke in 1940 with the code "337 1940". The "S.S." is not a new marking, not postwar applied and not the German marking for sS bullet. That rifle was exported to Sweden and the "S.S." marking was applied in 1940 by the Swedish inspector Captain Sten Stenmo. In Sweden they called the rifle "Gevär m/1940".