This is an awesome find, for those not on FB I'm copying some of the info provided by Matt Fox (BonsaiTreeEnt on here) - these finds are being displayed at his exhibition May The Toys Be With You in Leicester. The video confirms that these are Kenner produced hard copies which were sent to Palitoy, and used to make copper beryllium mounds which could then be used to produce the figures for retail.
"AMAZING NEWS: PALITOY PROTOTYPES FOUND! (video needs sound). Five 'hardcopies' have been discovered in Coalville and are now on display in the former Palitoy Factory as part of May The Toys Be With You exhibition. I hope the community shares in the excitement that I felt and enjoys the video that talks a bit about the discovery! Out of security consideration for these being displayed in a public space please refrain from discussion of value. These prototypes and more are free to view and enjoy from 2nd Nov to 10th Nov at Rothley House, Coalville Business Park, LE67 3NR. Additionally, Sat Nov 3rd 5pm author and collector Craig Stevens is delivering a talk, and Sat Nov 10th 5pm Bob Brechin and former Palitoy staffers are hosting a Q+A (tickets free, google 'Palitoy Eventbrite' to pre-book). Big thanks also to Ron Salvatore for advising on this find. New discoveries and great times for the hobby!"
"As I understand it, Palitoy received figures in bulk from the Far East for Star Wars and ESB toy lines - they packaged them in Coalville but weren't involved in the tooling of figures (they did tool the vehicles and playsets, and in fact I have a schematic from 1979 showing UK tooling of the Darth Vader TIE Fighter). When it came to 1982/83 there was a move towards 'consolidation' of the European operation - as we know Bi-Logo / Tri-Logo - and at this time Palitoy bore a bigger load. Hence the tooling of ROTJ figures for the European operation being handled through Palitoy. I believe the Beryllium moulds were still sent to the Far East though rather than figures made in UK. This may not be entirely gospel, and I'd probably need to quiz them over more specifics about what happened where and when but this was my interpretation."
"I believe there is some shrinkage when making the moulds, which necessitate the hardcopies being that bit bigger than the final figure."