This gundam paper model is a SD RGC-80 GM Cannon, a mass-produced artillery mobile suit, and a variant of the RGM-79 GM, featured in the original design series Mobile Suit Variations and in the anime series Mobile Suit Zeta Gundam, the papercraft is created by [unknown].
With the failure of the RGC-80-1 GM Cannon Test Type, the Earth Federation designers took the gathered data and developed the RGC-80 GM Cannon, correcting the problems encountered in the predecessor model.
Deemed successful and put into production in late UC 0079, the topweight balance and recoil problems suffered by the Test Type were addressed by mounting only one 240mm rocket-assisted projectile cannon and adding heavier armor to the hip skirt as well as the legs. The GM Cannon still possesses 60% parts commonality with the RGM-79 and could also carry the same hand weapons and shields as its general-purpose sibling. [Source: wikia]
You can download this gundam papercraft here: SD RGC-80 GM Cannon Free Gundam Papercraft Download [Box] [Gavitex]