I need help identifying this mechanical puzzle that consists of 6 pieces (see image) which I have to fit together into a sort of concave polyhedron.
This puzzle was designed by Stewart Coffin, and he called it the Star of David puzzle. It is a variation on the classic diagonal burr puzzle. The aim is to put the pieces together into a symmetric shape, and there are three distinct symmetric shapes you can make that have 3-fold rotational symmetry. One of these shapes looks like a 6-pointed star from one direction.
It has not been mass-produced, but only made in relatively small numbers by hand by puzzle craftspeople.
Here are some pictures taken from John Rausch's site:
Nowadays you can 3D-print puzzles like this.