This is an Alan west contactor,the plastic pots were oil filled dash pots intended to slug the overload trips on the motor starting surge.
Even if it has three poles you can use it on single phase by wiring two in series.
Dad had one on his ml7 many moons ago worked ok but tended to buzz a bit.
Also the thin oil tended to leak out over time.
Probably not so important with modern motors tthat can withstand overloads better than oldies.