The MS-04 Prototype Zaku was the first mobile suit to emerge from the mobile suit project of the Principality of Zeon.
It was later simplified for mass production as the MS-05A Zaku I Early Type.
Zeon embarked on an ambitious mobile weapons programme as part of its aggressive militarisation in preparation for war with the Earth Federation.
The first mobile suit design was the MS-03 Prototype Zaku. Due to performance problems, the design was scrapped as Zeon searched for a workable design. The MS-04 Prototype Zaku was an big improvement as it was powered by the newly-invented Minovsky fusion reactor. That doubled the power output and allowed the Prototype Zaku to function well enough to be used in combat.
Expensive and complex features were stripped from the Prototype Zaku to make it cheaper and easier to mass produce. This mass production model was the MS-05A Zaku I Early Type.
The MS-04 Prototype Zaku was a much improved version of the MS-03 Prototype Zaku. The newly-invented Minovsky fusion reactor was used to power the MS-04 prototype, providing it with twice the power of the MS-03.
The increased power output also meant that the MS-04 could be equipped with heavier armour, allowing it to be capable of being battle tested.
The Prototype Zaku only had a ranged weapon. The development of the prototype focussed heavily on the performance and mobility of the mobile suit. Hence, only one weapon was developed for use by the prototype before it was replaced by the mass-produced MS-05A Zaku I Early Type.
100 mm machine gun
The electrically-operated 100 mm machine gun was developed specifically for the Prototype Zaku. It was capable of rapid fire but dealt little damage against warships. This led to the development of a bazooka to combat warships.
The machine gun was later developed into the ZMP-47D/105 mm machine gun that was used by the Zaku I.
Behind the scenes
Kunio Okawara was the original mechanical designer.