My favourites among the listings are a series of molds for The Final Frontier figurines produced by Galoob. These were made by roto-molding, which Prop Store have an excellent description of in their auction catalogue:
Rotational molding or “roto-molding” uses liquid vinyl material to create items such as baby doll heads or squeeze toys. The molds are composed of one piece with an opening. A set amount of vinyl is poured into the opening, which is then capped and rotated in many directions while heated until the material forms an even, detailed coat on the inside of the mold. While still warm, the part is pulled from the mold and allowed to cool. Roto-molding is a very economical manufacturing method because the mold is cheap to produce and simple to use.All five character's in Galoob's Final Frontier range are available, Klaa, Sybok, Kirk, Spock, and McCoy, although most of the molds are missing parts, with just Klag and McCoy complete (I wonder if you could make your own figures from them?)
The molds themselves are made by submerging a wax pattern in a bath and electroplating onto it until the desired mold thickness is reached. The wax is then melted out of the mold, leaving the “clean” form inside. The inside of the mold is where the detailing lies; therefore, the exterior may only provide a marginal representation of the final toy.
