Part of the preproduction process. Once the mould for a figure is made, the test run of figures that comes from the mould are the first shot figures. They aren't always in production colours and don't have coos.
As far as I know, and I am no expert, the moulds would have been created by Kenner. The stages of production would be a wax sculpt. From this a mould would be created and Dynacast hard copies made from this first mould. These would be refined if needed and then a steel mould created from the hard copy. From this steel mould and at Kenner, the first shots would be made. Once the mould was signed off it would be sent to the Far East, along with all sorts of other bits to aid in production. The coo would be added to the mould. They would then go into production. Engineering pilots come out of these production runs and are for quality control.
Feel free to correct me if I'm wrong on any of this by the way.
Gus and Duncan's guide to prototypes is the book for the more curious.