Kalibak isn't the most popular Super Powers character, but if you look closely the figure certainly has incredible sculpting detail. The prototype shown here, a hand painted protomolded figure, exhibits that detail nicely.
Protomolded figures were created in house at Kenner using low yield aluminum molds. One distinguishing characteristic is the milky white plastic employed in their creation. They never possess dates, copyright information, or footholes. These prototypes were specifically used as paint masters, catalog/photography samples, and trade show display pieces. Based on noticeable paint loss on the feet bottoms, I'd put the use of this prototype in one of the last two categories described above. Obviously the figure was glued down to something at one point.
Here we see the foot hole absence as well as the paint loss from being glued down. Notice some glue is still present on the feet, although it has obviously dried out over the years.
The above picture provides a comparison with the production figure. The prototype stands on the left, while the production figure stands on the right. Side by side, the prototype's brilliant hand detail is strikingly evident. This prototype surfaced in a large find which included many Super Powers and Star Wars prototypes. The collection was consigned for an ex-Kenner employee by a well respected toy dealer in Cincinnati. This same find yielded all but one of the paintmaster figures with paint swatches showcased on this site.