This gundam paper model is a SD GX-9900 Gundam X (aka Gundam X, GX, X), a mass-produced mobile suit built by the former United Nations Earth, as well as the titular mobile suit of After War Gundam X, the papercraft is created by Storm of Dragons based on Turbolabo's SD Gundam series, and shared by yenc.
There are two feature versions of Gundam X. The primary featured one was piloted by Garrod Ran and later by Jamil Neate, after it was badly damaged in combat and was repaired and rebuilt as GX-9900-DV Gundam X Divider.
The second one was featured in the manga sequel, After War Gundam X: Under the Moonlight. The story featured a different Gundam X (adorned with teal colors) and its pilot was Rick Aller.
Built at the height of MS advancement by the UNE, the GX-9900 series is one of the most advanced MS of its time. The series was mass-produced and pressed into service near the end of the 7th Space War. After the environmental devastation at the end of the 7th Space War, MS development on Earth became stagnant as humanity recovered; Gundam X and its brethren Gundam series remains top-of-the-line after 15 years. Because the UNE no longer existed, there was no regulation over the Gundams and they found new life in the hands of the Vultures. It's because of Vulture-use that no two Gundam X are exactly alike.
The unit is purposed as an assault MS. It carries a powerful beam cannon known as the Satellite Cannon. The cannon requires power beyond what Gundam X is capable of on its own, so UNE engineers created the D.O.M.E. (DOME) lunar microwave facility to power it. When the Satellite Cannon is to be used, solar power collected at the facility is sent to the Gundam X via a microwave beam and stored in the large reflector panels mounted on the suit's back in preparation for a particle beam blast powerful enough to wipe out a MS squad with a single shot.
While the Satellite Cannon is indeed powerful, it also requires a lengthy time to charge-up and fire. Any enemy target with enough speed and combat capability can take such an opportunity to attack Gundam X and disrupt its ability to absorb the microwave beam. Furthermore, the system can only be used when there is a clear line-of-sight to the lunar power facility. Because of this, the cannon tends to be used only as a last resort or for long-ranged assault. UNE engineers equipped Gundam X with a standardized set of weapons: a large beam sword, four chest mounted vulcan guns, and a shield buster rifle (doubling as a shield as well as a beam rifle). This allows Gundam X to be adaptable and versatile in most combat situations. The Vultures (who have salvaged Gundam X units) also added optional equipment to the suit, including a holster shield of a buster sheath rifle and a torpedo launcher.
The unit was specifically designed to exploit the capabilities of its Newtype pilot, but also usable for regular humans as well. At the helm of a Newtype pilot and using the Flash System, the pilot can mentally communicate and access its remote controlled drone versions of itself, the FX-9900 GX-Bits. They're physically exactly the same as Gundam X, but has been refitted to be automated drones for the Newtype pilot to command. The amount of bits the pilot can use is relative to their natural mental powers; the greater their New-Type abilities the greater amount of bits it can use for combat. In combat, the bits are used for coordinated attacks to protect its master and can utilize the Flash System sequentially to fire its Satellite Cannon. Naturally, for its regular human pilot, the bits are useless as UNE engineers never created an alternative control system for normal pilots to exploit the full potential of Gundam X.
The series has no special abilities to secure itself from being stolen from enemy hands. The only thing required to activate the Gundam is its G-Controller. The G-Controller is actually part of the series's cockpit control system, but it doubles as a physical key to activate Gundam X. The key system itself isn't a strong security measure, more like a key to a car. Just like a car, it can be hot-wired. A skilled MS engineer can bypass the G-Controller's access key, allowing anyone with access to the cockpit to wield Gundam X, such as Garrod's Gundam. When NUNE (New United Nations Earth) engineers created GX-9901-DX Gundam Double X, they never changed the design of the access controls to the G-Controller. Anyone with a G-Controller from Gundam X can also use it to activate and control Gundam Double X.
For Garrod's unit, it was unfortunately defeated by a Newtype pilot utilizing RMSN-008 Bertigo. Its Satellite Cannon was damaged beyond repair and had no components to replace it. To compensate its most powerful weapon, it's equipment was upgraded with salvaged MS technology and redubbed as GX-9900-DV Gundam X Divider. The series would later be succeed by NUNE's GX-9901-DX Gundam Double X. [Source: wikia]