the edison diamond disc record is a type of phonograph record marketed by thomas a. edison, inc. on their edison record label from 1912 to 1929. they were named diamond discs because the matching edison disc phonograph was fitted with a permanent conical diamond stylus for playing them. diamond discs were incompatible with lateral-groove disc record players, e.g. the victor victrola, the disposable steel needles of which would damage them while extracting hardly any sound. uniquely, they are just under  in () thick.