The Siemens 3VA1040-3ED32-0AA0-ZD00 is a 3-pole IEC frame 100 circuit breaker from the 3VA1 series, rated for line protection with a fixed thermal-magnetic trip unit (TM210, FTFM). Its 40 A continuous rating (In=40 A, Ir=40 A fixed) means it protects a 40 A branch circuit; the short-circuit release is fixed at 10× In (400 A), so it clears faults above that threshold instantly.
The nut keeper kit included with this variant is specifically for DC Power OEM applications in China, so if you're building a DC power distribution cabinet, the kit saves sourcing a separate mounting accessory. The 3-pole configuration is typical for three-phase line protection — feed it from a busbar or cable, and it protects the downstream wiring and loads.