Cosmetic: Normal use and wear.
The engraving states: Seiki Optical Industry Co. Ltd. X-ray Indirect Photographing Device Army Noborito Laboratory. No 2 Section. No. 4 Group. The Army Noboruto Laboratory operated in Kanagawa Prefecture in Japan before and during the second world war from November 1937 until August 1945.
The earliest Canon X-ray prototypes were made during 1939 and early 1940 with a standard production model being ready by November 1940. The earliest models had Canon Seiki and eagle logo (as in these two examples) engraved on the top plate. The Canon Serenar lens came into use in 1942 or early 1943 starting with the 3xxx series. Wartime manufacture seems to have ceased in 1944. It resumed from January 1946. Dechert suggests that the Seiki X-ray Canon cameras range from circa serial 1950 to 6337.