M1 calculating disc. White bakelite. Numerous calculation markings. Two arrows for calculating distances. Central brass screw. Rule Slide M1 No 3707 Insp WPB 1943 markings. Manufactured by The Sillcocks Miller Company B 174703. Diameter 30 cm. Some wear and patina. Condition II+. M1 calculating disk White bakelite construction with numerous calculation markings and two arrows for distance computation. Brass central screw. Marked Rule Slide M1 No 3707 Insp WPB 1943, made by The Sillcocks Miller Company B 174703. Diameter 30 cm. Showing expected wear and patina. Condition II+.