The Siemens 5SY5204-6CC12 is a 2-pole miniature circuit breaker from the 5SY5 series, rated B4 curve with a 440V DC breaking capacity of 10kA. The B4 curve (4x In magnetic trip) suits cable and semiconductor protection in DC circuits where inrush is moderate.
Snap-on DIN rail mounting for standard 35 mm rail. The 2-pole width (2 modules at 18 mm each) fits a standard distribution board or sub-panel. Rated for 440V DC, so it's sized for DC-side protection in solar combiner boxes, battery banks, or DC motor drives — not for AC branch circuits.