The Siemens 3VA1120-4GD42-0AA0-ZD00 is a 4-pole IEC frame 160 circuit breaker with breaking capacity class S, rated Icu=36kA at 415 V. The thermal-magnetic trip unit (TM210) is set with a fixed overload Ir=20 A and a fixed short-circuit pickup Ii=16 x In (320 A), so it's a dedicated line-protection device for a 20 A circuit, not adjustable in the field.
The 4-pole configuration with 100% N conductor protection suits three-phase plus neutral distribution in IEC-based switchboards — common in OEM builds for machinery or sub-distribution boards. The included nut keeper kit is a detail for DC Power OEM applications in China, meaning the factory-assembled busbar connections stay torqued under vibration.