This is a hinged, spring loaded clip that fits in a square hole, and holds a coin.
I use these to hold down the edges of warped panels on my buildlog.net laser 2.x laser cutter bed, which is a grid of half inch squares, a half inch deep.
But I expect you'll find other uses for this. Lots of square holes out there. The SCAD file lets you configure the square size and depth, coin size, and how high the coin is held above the surface.
Typically the hinge is fused on the bottom layer after printing. Just gently squeeze the top and bottom of the clip alternately to crack it free.