This is the belt buckle for the Canto Bight Police Officer uniform. The file "left_chamber_v2" is intended to be attached to the belt leather (6 to 7oz leather) using Chicago screws, most likely a 1/4 thick Chicago screw. After you've attached that to the belt, then the file "buckle" should clip onto that piece and slide down so the square hook-looking piece locks into left chamber. I plan to glue mine permanently and have all belt adjustment in the back of the belt. This shouldn't be considered a functional belt buckle.
UPDATE (12/21/2018) - Use the V3 versions of the buckle and left chamber. Sized better for the 3.75" wide belt.