The prototype stage seen here is referred to as a hardcopy. Obviously the character is the 3rd series Cyclotron. As the vibrant and detailed paint job suggests, this prototype is entirely hand painted. Cyclotron, like all other hardcopies, was hand cast using silcone molds.
This is the exact Cyclotron prototype used for photography in the 1986 Toy Fair catalog. The above photo shows the prototype in use many years ago. Notice Cyclotron's mask is glued into his right hand in the catalog photo. Paint loss is evident on the hardcopy's mask today, exactly where the mask was once glued into the hand man years ago! The history of the piece is well documented and adds to the appeal of this prototype. It's pretty amazing to see something like this still in existence 18 years after the hardcopy served its ultimate purpose.
In the left photo one can see the figure's back exhibits a small hole for placement of a pin. During the catalog shoot, figures were mounted onto a board for photography. This clearly explains the presense of the hole. The right photo affords a torso shot with Cyclotron's mask removed. Although the mask shares the same hand painting of the hardcopy, the material differs in that it is a milky white plastic. I would classify the mask as a protomolded piece since it appears to have been cast from a low yield aluminum mold as opposed to a silicone mold.
This shot shows the Cyborg hardcopy completely disassembled, a characteristic indicative of hardcopies. The head, limbs, and hand pieces all connect to their respective areas through the use of plastic pins. Small metal dowels are commonly used for attachment on hardcopies too.
Many of the prototypes used in the '86 Toy Fair catalog photography session were resin hardcopies, while a few were internal first shots cast from low yield aluminum molds. Samurai and Mr. Miracle were both IFS's, while Cyborg, Golden Pharaoh, Tyr, Mr. Freeze, Orion, and Cyclotron were all hardcopies. I'm uncertain which material Plastic Man and Shazam were cast in as those two represent the only 3rd series characters that haven't surfaced from the photography shoot. Check out the 1986 Toy Fair Catalog to see the full pages.