The Siemens SENTRON 5SM3315-0KK is a 2-pole residual current circuit breaker (RCCB), type AC, rated 125 A with 30 mA trip sensitivity on 230 V AC.
Supply can enter from top or bottom — no forced busbar orientation.
The 10,000 mechanical cycles typical service life is standard for a residual current device in this class — not a daily-switching contactor, but fine for the occasional test-button exercise and fault clearing it sees in service. Silicon-free construction matters for environments where silicone outgassing can contaminate contacts or optics. Overvoltage category III means it's rated for fixed-installation level (distribution board, not downstream socket).