The Siemens 5SY4603-7CV is a miniature circuit breaker (MCB) rated for a short-circuit breaking capacity Icu of 15 kA at 400 V AC, in a 3-pole plus neutral (3P+N) configuration with a C-curve trip characteristic and a 3 A rated current.
Snap-on mounting to DIN rail EN 60715 — standard 35 mm rail. The 3P+N form factor occupies four modular widths (4 x 18 mm) in the enclosure. For a panel OEM, that's a known fill factor; no surprises on the gland plate layout.