This spectaular piece is referred to as a wood pattern. A wood pattern is the initial stage of a vehicle's life in the production process. This is quite a different medium from the initial stage of an action figure, which begins as a wax sculpt. You'll notice the guide board is present which encompasses the wooden ship.
Above we see a second view of the pattern. You'll notice is has a grey primer covering the ship portion. This masks the wood grain underneath. I was unable to learn the reasoning for the primer's presence.
Here we see yet another view. The front battering ram, top middle fin, and ship bottom were done as separate patterns as far as I know.
Above we see a final shot of the wooden ship. Patterns often exhibited detail added on with bondo. However, the Supermobile was a fairly sleek, non-detailed ship so this was not necessary. A piece like the front battering ram may have had extra detail added on in this manner.
Wood patterns are incredibly rare finds. Many were utilized as firewood after serving their purpose, while others were taken home and hung on employee walls as abstract art. I heartily agree that these are true works of art. This piece and the Hall of Justice wood model shown on this site are the sole creations of Kenner pattern makers that have surfaced for the Super Powers line.