Siemens Sentron Handle Locking Device for use with 3VA2 100/160/250/400/630, 3VA2/3 100/160/250/400/630, 3VA5 400/600,

The available interlocking devices can be used to implement a mutual interlock between at least two 3VA molded case circuit breakers.
The interlocking device only ever releases one 3VA molded case circuit breaker at a time, thereby ensuring that only the released circuit breaker can be operated.
All other 3VA molded case circuit breakers remain in the safe OFF (O) position and are blocked by the interlock.

Siemens 3VA MCCBs and accessories