The Edison Diamond Disc Record is a type of phonograph record marketed by Edison Records from 1912 to 1929. They were named Diamond Discs because the matching Edison Disc Phonograph was fitted with a precision-made semi-permanent diamond stylus for playing them. Diamond Discs were incompatible with ordinary disc record players, the disposable steel needles of which would damage them while extracting hardly any sound. Uniquely, they are about 1/4 inch (6 mm) thick.
Edison had previously made only phonograph cylinders but decided to add a disc format to the product line because of the increasingly dominant market share of the shellac disc records (later called “78s” because of their typical rotational speed) made by competitors such as the Victor Talking Machine Company. Victor and most other makers recorded and played sound by a lateral or side-to-side motion of the stylus in the record groove, while in the Edison system the motion was vertical or up-and-down, known as “hill-and-dale” recording, as used for cylinder records. An Edison Disc Phonograph is distinguished by the diaphragm of the reproducer being parallel to the surface of the record. The diaphragm of a reproducer used for playing ordinary records is at a right angle to the surface.
In 1929 Edison also produced a short-lived series of ordinary thin lateral-cut “needle type” disc records