The aluminum plate is a custom made part for the Supertrooper and Pre-Pro #1 automatic blaster. The first piece is very similar to the jetpack adjustment knob, but it's smaller in size, which might be a found part or a custom made part. The second piece is a Glenross dental expansion screw, the same piece used on the left gauntlet too. The third pieces are still unknown, but might be part of some electronic device. The fourth piece is actually the sawed off 'reset' side plate of a Casio MQ-1 calculator.
The images of the printed model were posted by 01Hawk over at the TDH forums and I posted them here with his permission.