We have several Edison Amberol cylinders in our Technology through Time Collection.
Early cylinders for phonographs were made of wax. They were hollow and had audio recordings engraved on the outside of the cylinder. They were produced between 1896 up to the early 1910s, at which time flat disc records became more popular and the use of cylinders declined.
Thomas Edison introduced the wax Amberol cylinder in 1908. These cylinders doubled the number of grooves on an equivalently sized wax cylinder and so the playing time twice as long as that of the Gold-Moulded cylinder (four minutes rather than two minutes). Edison Amberols are marked with "4M" ("four minutes").