Are you sure there aren't any marks on the underside of the tube? A lot happened in 1945 but there may have been a calibre stamp. Is the stamp "Gebrüder Heym"? Bruno & Richard Heym were at the helm by the start of WWII. Folklore has it that the design of the 7x75R E.August Vom Hofe commenced in 1939.

Kind Regards,

Raimey
rse