The figure that would become Optimus Prime started out as Diaclone Battle Convoy from Takara. It was originally intended to be a piloted mecha, hence the many seats for small pilot figures in both the tractor and the trailer. The original release in 1984 knows many different variations due to being produced in different factories. These differences include (but are not limited to) the size of the fists, the shape of the gun barrel, the colors of Roller, the Combat Deck missiles, and the gas pump, as well as the color of Optimus´ feet.
Diaclone also upgraded this toy with a new trailer as Powered Convoy, the toy that would eventually become Ultra Magnus. Both the original Optimus Prime as well as Ultra Magnus have been re-issued numerous times and we have also had various incarnations in black (Nemesis Prime / Black Convoy) and other colors.