Early example of a Sigma mechanical comparator with workings visible. Made 1945-1955 Early example of a Sigma mechanical comparator circa 1940
Sigma Instruments thickness gauge, 1951 stored in a box and fitted with a inspection fitting for measuring screw thread acceptibility. Purchased from Plessey Records in 1951. Sigma Instruments thickness gauge 1951
Sigma mechanical comparator fitted with a perspex cover to reveal workings and with the original instrument cover; complete with an inspection fitting on the instrument platform; dated 1940 to 1950. Sigma mechanical comparator 1940-1950
