The Siemens 5SM3312-6KK12 is a 2-pole residual current circuit breaker (RCCB) from the SENTRON family, designed for 230 V AC, 50 Hz systems.
The 25 A rating holds at 40 °C and 45 °C; above that it derates linearly to 17.5 A at 70 °C. The breaking capacity is 0.5 kA per EN 60898 and IEC 61008-1, which covers domestic and most commercial fault levels; for higher prospective short-circuit currents you'd need an upstream MCB or fuse to coordinate. Surge current resistance is 1 kA, so it withstands the inrush from capacitive loads or nearby lightning-induced surges without nuisance tripping.
Snaps onto a 35 mm DIN rail (REG profile), occupying 2 width units (36 mm). Depth is 70 mm, height 90 mm. The supply connects at the bottom.