The 5SL6105-8CC: The 6 kA breaking capacity at 230/400 V tells you this breaker can safely interrupt a fault current up to 6,000 amps. The 0.5 A rating is unusual — you'd typically see this on a control transformer primary or a small signal supply, not a general lighting circuit. The D-curve (10-20x In magnetic trip) keeps it from popping on the transformer's magnetizing inrush.
Sourcing this part
Because it's an active catalog item, the 5SL6105-8CC is sourced through Siemens' standard distribution network. No need to hunt surplus channels for this one; it's a regular production breaker.