Google Japan's concept keyboard is inspired by rotary phones

"Instead of keys, the Gboard Dial Version keyboard features various alphanumeric characters and functions laid out beneath a series of nine dials of various sizes, including one just for the return key. To type a specific character, you stick your finger in its corresponding hole and then rotate the dial until you reach its limit. When you release it, the dial rotates back."

"Rotary phones used a technique called pulse dialing, where a spring-loaded dial generated a series of electrical pulses as it rotated back to its home position. The phone company would decode those pulses to determine what number was being dialed. Google Japan's Gboard Dial Version trades pulse dialing for modern sensors that translate each dial's rotational movements into USB signals."

Google Japan created the Gboard Dial Version, a keyboard that replaces keys with nine rotary dials arranged over alphanumeric characters and functions. Users type by placing a finger in a character's hole, rotating the dial to its limit, then releasing as the dial springs back. The design uses modern sensors to translate dial rotation into USB signals rather than historical pulse dialing. An accompanying mouse stand disables the webcam when a mouse is placed on it. The Dial Version is not sold, but the design is open-sourced on GitHub with 3D printer models, PCB designs, and a parts list for DIY construction.

Read at The Verge