The Small Microverse Projector quest asks for 15 Machine Casings, but to complete the structure 16 casings are required.

The quest also doesn't contain any text explaining how to build the structure or what it is used for.

It is also worth noting that the JEI preview of the Small Microverse Projector cannot show the top layer when viewing one layer at a time. I had to figure out what to build there based on the 3D model.