If my memory is correct Disney outsourced the original chests creation at a cost of $60,000. Every single rivit and detail was individually hand crafted. Then when it came time to have moulds made the person hired to do that work, for some reason started to mold everything individually as well! Rivits, tentacles, edging... It was never going to reach completion. So that was scrapped and that job went to another shop as filming had already began. There was one main hero chest that was taken apart and molded. A top, bottom, separate hinges in the closed position, the inner locking mock up mechanism which was a solid piece, handles left and right and then for the open chest separate locking blocks were cast to compensate. The crab lock was a separate piece adhered on which also had a couple different moulds made. There was a one piece crab and another version with separate arms and legs for the opening gag. The section where the crab mounts was cast separate as well for open chests. When all was said and done the original mould was marked so any future pulls could be identified. This marking is on the MR version as theirs was based off a pull from that mould.
An interesting foot note is the chests on display at the film premieres and Disney parks were originally created for that soul purpose but some did end up used in filming and then on the rides themselves. No chests were made from wood. All were rubber or cast plastic. There was an issue with the opening chest gag as it wasn't designed to actually open as seen in the film. That chest was full of plungers with cables wires and tubes coming out of one end. It was a challenge to get all that to work in a tiny confined space. The same guy that did the rotating map gag did that work.
There was also an issue with the key actually fitting the lock. It was never ending.
Forgot to add the chests anded up with hand made handles for most of them. Others had castings. Any open chests also had hand made hinges.