MAM-07-X3 Grabro Underwater Bit-mounted Prototype

By Jenxi Seow



The MAM-07-X3 Grabro Underwater Bit-mounted Prototype was an experimental underwater mobile armour developed by the Principality of Zeon.


The MAM-07 Grabro was one of the earliest mobile armour used by the Principality of Zeon during the One Year War. It was developed with the MA-05 Bigro as the basis of its design. It took the MIP Company one and a half months to complete the Grabro.

Three units were constructed in the submarine dock of California base and testing was conducted in the Gulf of Mexico.

One Grabro unit was fitted with a psycommu system and its claws were replaced with underwater-use bits. The experimental prototype was designated the MAM-07-X3 Grabro Underwater Bit-mounted Prototype. It proved to be successful, sinking two Earth Federation ships within an hour. However, due to undocumented reasons, the design was used and the prototype was later restored to the original design.


The MAM-07 Grabro was a part-submarine, part-mobile suit designed for underwater combat. The MAM-07-X3 Grabro Underwater Bit-mounted Prototype had its claws replaced with underwater-use bits. Its rear fuselage equipped with transmission units that controlled the bits. It was fitted with a Quasi-Psycommu system to allow normal pilots to operate the bits. A sonar dome was attached on the bottom of the unit to increase its sensing range.

MAM-07-X3 Grabro Underwater Bit-mounted Prototype bottom view

MAM-07-X3 Grabro Underwater Bit-mounted Prototype bottom view


The Grabro prototype only had no close-range weaponry. It was equipped with underwater-use bits, torpedos for ship-to-ship and ship-to-shore attacks, and surface-to-air missiles against airborne targets.

Seven-tube torpedo launcher

The two seven-tube torpedo launchers mounted on the main body of the Grabro carried three rounds in each tube. This gave the mobile armour a total of forty-two rounds to attack enemy ships or submarines, and coastal targets.

Surface-to-air missile launcher

The Grabro had two surface-to-air missile launchers mounted on its main body. Each launcher had eight rounds that were used to take down enemy air units.

Underwater-use bits

The bits were remotely controlled guns. Each bit was mounted on each side of the Grabro, where the claws used to be. The Quasi-Psycommu system allowed the pilot to control the bits and the control module handled the transmission of data to the bits.

These bits were not as fast compared to space-use bits. However, limited test data proved that they were deadly additions to the Grabro.

MAM-07-X3 Grabro Underwater Bit-mounted Prototype top view

MAM-07-X3 Grabro Underwater Bit-mounted Prototype top view

Known pilot

  • Unknown

Behind the scenes

Kunio Okawara was the original mechanical designer.