Summary

It is a holster for light gun arcade.
It is valid for guncon2, g-con 45. aimtrak, etc-
In the g-con 45 all pistols are available.
In the guncon2 model it is narrower, the guncon2 enters the upper part, see image.
It has optional spacers and letters to cover the holes.
You can see more here:
https://youtu.be/MdWdKdPZYJc