What is the principle of French measuring ball egg opener?

This thing is a new thing, which is quite funny. The simple thing of opening an egg makes him like a project, which is interesting.

I guess there is a small cutting edge on the inner edge of the bell-shaped cover. By the impact of the steel ball, a circle of dents or something like the edge of a stamp is engraved on the egg shell, and then it is neat after being broken. Egg shells are brittle and easy to crack along the damaged parts, so the trimming should be very neat.

such a melodramatic thing should be more useful in hotels. Open eggs look good.