It is split hole puncher. It is used for punching for metal plate. It is popular in electricity industry, construction, etc. It need to work with a pump.
It could punch 0.41"(? Hydraulic Hole Punching Tool CH-700 apply to L and H style flat copper and busbar. End is designed with flat seat, smooth and not fall. Single oil return, punch dies made of high carbon tungsten steel and not easy to wear off. 1Hydraulic Hole Punching Tool 1concave pressing plate.

(one of the four is in the puncher).