This mech paper model is Catapult, an offense oriented, second-line fire-support BattleMech initially produced on a limited contract for the Terran Hegemony, from the real-time tactics video game MechCommander 2 of the BattleTech/MechWarrior franchise, the papercraft is created by Tirick Fire, and the scale is in 1:1000. The size of finished model is about 16 (H) x 12 (W) x 11 (D) mm.
Representing Hollis Incorporated's first foray into the 'Mech market, the Catapult was produced in record numbers over its initial three-year period from the company's brand-new, state-of-the-art factory. However, when the contract came up for review in 2563, the Hegemony decided not to renew it; while the Catapult had performed adequately at its role, it was not quite what they wanted. With large numbers of the 'Mech still in the field, the Catapult would continue to see use in the Star League Defense Force with second-line and specialist formations such as mountaineering regiments. When the factory constructing them switched over to the more-successful BattleMaster, Hollis' limited production of spare parts couldn't keep the design's numbers from dwindling.
When the Star League fell, many of the remaining Catapults joined Aleksandr Kerensky on his Exodus. The Capellan Confederation collected most of the Catapults that remained in the Inner Sphere, and the Hollis factory on Corey briefly produced new models and spare parts. At the same time, the Draconis Combine managed to seize a sizable force in their capture of Dieron. The renewed production ended when the Corey factory was destroyed at the onset of the First Succession War, ensuring the rarity of the Catapult during the rest of that bloody era. Entire invasions were commenced simply to seize the remaining number of these 'Mechs, particularly those launched by the Federated Suns against the Confederation.
Many variants of this venerable design were produced through its lifetime, and the Catapult's rarity began to reverse in 3033 when Yori 'Mech Works was contracted by the DCMS to produce the completely-revamped CPLT-K2 on Al Na'ir. The greatest change to the chassis came later, with the introduction of the CPLT-C3, which swapped out the original's LRMs for much larger and more powerful artillery missiles. These models were put to excellent use, especially when paired with Ravens, and paved the way for new design advancements.
In the years prior to and after the Clan Invasion, the Confederacy and Combine retained the largest number of existing Catapults, though many Periphery realms would field some of the centuries-old models, and more variants would be produced for decades. [Source: sarna]
You can download the papercraft model here: MechCommander 2 - Catapult Free Mech Paper Model Download