Carefully sand the case top and bottom making sure not to scratch them, the side rings will be hidden so scratches aren't so much of a problem but they are fragile so don't put too much pressure on them.
Some of the bolt holes are routed tight to form a rigid case, you may prefer to enlarge them a little to make assembly easier.

Top row, from the left:
PCB ring
Bakelite top
Wide quarter rings
Middle:
Wide ring
Base
IR plastic lid
Narrow rings
Half ring
Bridge,back and feet
Bottom:
Wide half rings
Narrow half rings
Narrow quarter rings