The Swing Key Case by Japanese design studio Claustrum in 'Leather Black Out' finish.

High Strength Stainless Steel Hairline Blackening Finish + Leather.
Fits ± 4 keys + extra ring.
Opens with one-hand operation.
Each piece is unique.
Made in Japan.

Size: 84 * 33 * 17mm

Weight: 38gr

Curious how it works?
https://youtu.be/1yu5VmKl_OE