[Would you like to see this in-game?]
TL;DR: The first prototype of the Chi-Nu equipped with a Type 90 75mm field gun.
Note: This is the only picture I could find of this tank. If you have any other significant information, please let me know.
History:
By 1943, it was very clear that Japan’s Ha-Go, Chi-Ha, and Chi-Ha Kai tanks were, quite frankly, obsolete when it came to tank-on-tank combat. This observation was further substantiated upon the reception of information of the relatively new M4 Sherman tank, provided by Germany. Should they be faced with this tank, they would have no appropriate counter. It was evident that development of a new tank was absolutely necessary, however, tank development required time and resources that the Japanese did not have. As such, an expedient project was put into place while more permanent measures were developed. This expedient project would be called the Chi-Nu and was to be based on the hull of the Chi-He, which was developed as an improvement of the Chi-Ha/Chi-Ha Kai. This decision would ensure that the Chi-Nu would share a lot of its parts with its predecessors, thus making it easier to produce. The turret ring of the Chi-He hull would be enlarged, allowing the tank to accept the turret initially designed for the first Chi-Ri. In this turret would be the 75mm Type 3 cannon, developed from the 75mm Type 90 field gun, however, when the time came around to actually construct the Chi-Nu prototype, the Type 3 was either not ready or not present. Short on time and options, it was eventually decided to just put a lightly modified Type 90 into the turret so they could get along with testing. The tank would pass its trials and see up to 166 vehicles produced, though these would not see service as Japan would surrender before they could be used.
Place In War Thunder:
Functionally, the Chi-Nu Prototype is identical to the production Chi-Nu we already have in-game, however, that production Chi-Nu is literally 1 of only 2 of Japan’s 3.3 ground vehicles (In RB). The Chi-Nu Prototype could act as a line-up booster, giving 3.3 Japan more longevity in a battle. Playstyle would be identical to production Chi-Nu, making it a great backup vehicle. Considering the aforementioned, the best place for the Chi-Nu prototype is the tech tree, being either before or foldered with the production Chi-Nu.
Specifications:
Armament: 75mm Type 90 cannon and 2x 7.7mm MGs
Dimensions: 18800kg
Weight: 5.64m, 2.41m, 2.68m (L,W,H)
Armor: Same as Chi-Nu in-game
Crew: 5
Ammunition: Same as Chi-Nu in-game
Speed: 39kph
Horsepower: 240hp
Sources:
Type 3 Chi-Nu medium tank - Wikipedia
SENSHA: [WT] Type3 Chi-Nu
https://tanks-encyclopedia.com/category/ww2-japanese-medium-tanks/