The advantage of being delayed ... I read some responses but I stopped after that of @onceuponatime. I understand that I will not know the true purpose of Item X.
I also stopped myself from being influenced by the opinions of others ... so I apologize if anyone else found the same use.
I believe the device, which resembles a detonator, was used in ammunition factories. It checks if the projectiles work!

Hold the vise by a support, place the projectile in the holder and then pull the lever with power.

This reminds me of a joke: A man was walking through a village and shouting that he castrated horses. A villager, interested in this, asked him how he did.
The man tells him: Put the "objects" between two bricks and hit one another with power!
Oh, says the villager ... but does not hurt?
The man answers: Yes, only when I catch my fingers!