This is a Merlin Gerin Masterpact M16N1 Circuit Breaker rated at 1600A/690VAC (Roughly 1.9MW 3-phase energy!) here is it tested against a C10A 1P+N MCB to withstand a 50kA short-circuit current from a 2500uF/2kV energy discharge capacitor!
The capacitor used is a Maxwell Energy Discharge capacitor that you can read about here
Some product series data and the full article with teardown and all pictures is found here:
The Masterpact M series circuit breaker is used to protect and control low voltage distribution systems. It can be installed in main LV switchboards (incoming units, main and secondary outgoers).
Nominal current: 800 to 6300A AC
Breaking capacity from 40 to 150 kA rms
Voltage rating: up to 690 V
Versions: 3 and 4-pole. Fixed or drawout.