The Masterpiece Optimus Prime Trailer from Justitoys. Supposedly limited to 4999 pieces in production. This came out about a year before Takara rolled out the MP-04
The finishing and etched trailer designs are flawless. No paint spillovers whatsoever.
The “Diecast parts” are actually just two rods in front of the trailer.
Insides have “humps”. for locking in Binal Tech TFs…. Just be careful with the tailgate locks, they look like they might break or snap off, filing them down so they open more easily would be a good idea.
Not all BT’s can fit inside, Grimlock, Sideswipe, Smokescreen, Streak can’t fit. Hound, Overdrive, Jazz can fit though. I tried inserting Tracks diagonally and then rotating him slowly and he seemed to fit, but I don’t recommend doing this on a regular basis.