Drum Selector

Telephones with drum selectors have a cylinder that is rotatable about a horizontal axis instead of a dial. The drum has the ten digits corresponding to ten indentations; The user puts a finger into a recess and thereby rotates the cylinder downwards until the stop is reached. After releasing, the cylinder ran back again.

I've seen this style of dial illustrated in early human-factors study reports. I didn't know they actually made them! pic.twitter.com/z1Z9CHhQOD

— Museum of Comm (@museumofcomm) March 19, 2017

Der Trommelwahlers were made by Siemens & Halske in Germany in the 1950s.

Via