>>23414949 (OP)
Vaguely GM-esque artillery type, lovingly named the RGM-79P-TOW, or "Tow-Jim"
Missile rack on the back is designed to tilt up for accurate artillery fire, while the knees contain HEAT missiles for short range engagements. Standard beam spray gun.
Extra ammo stores behind the cockpit and in the thighs is belt fed into the missile racks.
100% an experimental support unit, I envision it being used in 0081-0083 to fight Zeon insurgents in North Africa/middle east. Only a handful were ever made, they were too prone to exploding and critical misfires and too heavy too keep up with the Powered GMs and eventually GMII to be worth producing, however the missile racks were utilized later in the UC as optional attachments for Jegans and Jestas.