Sometime before the First Modern War, the Rebel Army required an affordable tank that would have a good range of mission profile, with balance between firepower, mobility and survivability. They already knew that what was left of the Regular Army was already producing and amassing a fleet of their own SV-001s, and Girida-O was meant to be its direct opposition. Even though classified as an MBT, Girida-O fills the role of a medium tank, complementing heavier tanks still in service such as Di-Cokka or Iron Iso. Girida-O sacrifices protection in favour of a smaller frame and faster speed. Due to design flaws, tank operators often ran over their own infantry support. In the course of the Modern Wars, the tank has seen a number of improvements.
Girida-O's chassis is utilised by the Rebel Army for other purposes, such as material transportation and bulldozing. A utility variant with the turret removed and equipped with a front bulldozer blade and a hydraulic dumper named Dararin Dara Dara is the primary transport of materials of the Rebel Army.
Other factions later involved in Girida-O's production are the Amadeus Syndicate and the Ptolemaic Army. The latter faction based on data stolen from the Rebel Army has developed its own variant (Ver. P.M.)  with improvements over the original, such as better armour protection without sacrificing mobility, as well as a superior cannon with an improved loading mechanism and higher stopping power. Additionally, the problem of situational awareness of the crew (that had plagued the original model) has been fixed, reducing infantry accidents to a minimum. The resulting AFV is also more expensive to manufacture.
The Girida-O is a tricky tank to defeat, due to its cannon shells flying in an arc and its speed. One of the few ways to fight it is to go very close to it and crouch, then continuously shooting at it. However, there is a risk of being ran over by the tank. Another way is to stay out of its line of sight and shoot it from afar. Using grenades is recommended.
|Girida-O: the original, most common variant.|
|Girida-O (Universal Metal Slug)|
|Girida-O "Dararin Dara Dara": a utility variant that can dump I-beams onto players.|
|Girida-O (Metal Slug 3), fires more shots than the original. This variant first appeared in Metal Slug on the back of the Iron Nokana.|
|Girida-O: an improved variant that fires more shots. Only appeared in Metal Slug Anthology.|
|Girida-O Ver. P.M.: a Ptolemaic variant that is faster and better armored.|
|Future Girida-O: an improved variant that is faster and better armored. It fires magnetic shots that can pierce through weak rocks and can make the latter crush the player near them.|
- Girida-O's design is largely influenced by American tanks of World War II.
- (Found in Metal Slug 6 standalone, not in anthology) An early concept image depicts Girida-O with a mine plough and a machine gun on top of the turret. Its treads are similar to the Di-Cokka's.
- The early concept depicted at the right resembles a M4A3 Sherman Jumbo with frontal track skirts, though it looks plump.
- Single-shot Grenade_launchers are mounted on Girida-O's turret, however those are never used on-screen.
- This tank is currently the only one whose chassis had been re-purposed for utility.
- Its treads in the game are similar to the SV-001 (Metal Slug).
- The original Girida-O's cannon goes back from recoil when it fires. However, the Ptolemaic variant's cannon goes forward instead when it fires, giving it a little more range.
- A Girida-O also makes an appearance in a cutscene of Metal Slug 3D being driven by Allen during an assault at a Regular Army base where it and several Di-Cokka's fire missiles towards Eri and Fio, killing both of them.
- ↑ Metal Slug Attack unit description File:MSA_Screenshot_unit_Girida-O.png
- ↑ Metal Slug Anthology (Wii) Introduction Manual, p.9 - Game Overview: Metal Slug
- ↑ Metal Slug Attack unit Stats
- ↑ Metal Slug Attack unit description File:MSA_Screenshot_unit_Girida-O_Ver._P.M..png
- ↑ Metal Slug Attack unit Stats
|Combat||Di-Cokka | Bull Chan | Girida-O | Iron Iso | Melty Honey | MV-280B | Mini-Bata | M-15A Bradley | LV Armor | MV-280C | Japanese Tank Soldier|
|Support||MV-280A | Dararin Dara Dara | 3-ton Utility Truck | Landseek | Nop-03 Sarubia | M-3 Rocket Launch Support Van | Double-Decker Bus | MG-36 | Ferry Boat | Subway | Turrets | Morden Saucer | Walking Locomotive | Garbage Fortress | Mine Carts|
|Aerial||R-Shobu | MH-6J Masknell | Flying Tara | Eaca-B | Null Fighter|
|Marine||Hammer-Yang | Jet Hammer-Yang | U25U | Mini-Sub 88|
|Vigilance||Mosque Artillery | Patrol Robot | Supervisory Camera | Sensor Mine | Morden Robot | Metal Mole | Laser Drone | Pods | Rebel Walker | Balor|
|Ptolemaic||Black Hound | Hover Vehicle | Hover Unit | A.P.C. | Ptolemaic Slug | Wall Drone | Units | Ptolemaic Saucer | Mammoth Tower|