The Siemens 3VA9257-0GX01 is an auxiliary switch module with a rotary operator mounting adapter. It mounts on the side wall of a 3VA10, 3VA11, or 3VA12 molded case circuit breaker.
The 'rotary op. mounting adapter' in the description tells you this is not a standalone auxiliary switch you wire into the panel. It's a mechanical adapter that lets the auxiliary switch physically couple to the rotary operator mechanism on the breaker's side wall. If you are retrofitting a 3VA breaker that already has a rotary handle, this module snaps onto the side wall and its contacts change state when the breaker trips or is manually switched. The product class B restriction means Siemens routes this part through their partner channel — you won't find it on an open shelf; it's quoted per order.
Integration Note
Mounting is side-wall, not front-panel. The adapter interfaces with the rotary operator shaft on the breaker's side. Verify the breaker frame size (3VA10/11/12) matches before ordering.