The ST-A3 was the third and last finished prototype for the Type 61. Being part of the second phase of development for the Type 61, together with the ST-A4 it overcame the transmission problems the ST-A1/2 had, and the overall vehicle design was pretty much the same as the final production model. While the ST-A4 was a later prototype, it was completed earlier than the ST-A3, and due to the ease of manufacturing and enlarged cupola became the basis for the Type 61 MBT. This left the ST-A3 behind as a promising prototype incorporating an autoloader.

The ST-A3 was introduced in Update "Hot Tracks". While very similar to the final product being the Type 61 MBT, it comes with a 6-second autoloader with a first-stage of 11 shells, which makes it essentially a Type 61 with a 1-second faster reload regardless of crew damage. For tank combat, the ST-A3 in War Thunder has a commander cupola that is less at risk of being hit due to its small profile, the machine gun coming with a gun shield offers some spalling protection to the HMG and offers slightly higher elevation making for a better anti-air defense.