That 63 A holds all the way to 50 °C ambient — no derating needed in a warm panel — then steps down gradually to 53.55 A at 70 °C.
The auxiliary contact version ships with 2 HQ auxiliary switches, and the shunt trip (STL) release is built in as the auxiliary release design.
The 63 A rating at 40–50 °C is the working number for sizing a feeder or main breaker in a panel that sees ambient heat from transformers or drives. The interrupting ratings — 242 kA at 240 V, 187 kA at 415 V and 440 V, 121 kA at 500 V, and 4 kA at 690 V — tell you this breaker can clear a bolted fault on a high-capacity utility service without blowing apart. The ETU350 release is adjustable, so you can set the long-time pickup and short-time delay to coordinate with downstream breakers. Power loss is 5.4 W maximum — negligible for thermal budget in a crowded enclosure.