Also known as: オイ車, mi-to
The O-I Super Heavy Tank was a prototype Tank developed by the Imperial Japanese Army in World War II. The vehicle featured a multi-turreted design and an immense weight of 150 tons, second only to the Maus (Tank). While stronger than any available Japanese tank at the time, it's immense weight and size made it unfit for the Pacific theater, with only one turret-less prototype being developed for trials.
However, despite design, it is able to carry a 12cm gun or the Derp 15cm Gun, which these guns are taken from the Japanese Navy guns themselves. the O-I line got also has been rebuffed during WoT 2.0, Including the famous Type 5 Heavy having its armor back.
While only the O-I was produced, this tag can refer to the variety of paper (albeit later confirmed fake) design related to the O-I popularized by World Of Tanks, including the O-I Exp., the O-Ni (Tank), the O-Ho (Tank), etc.