Silly thing :

The success of the PT-76B prompted the development of a more powerful version. The Object 906 retained the same characteristics of the PT-76B: stabilized, amphibious and very light, but with a more powerful 85 mm cannon. It never went into service or serial production, but if it had, it would have received the designation PT-85. The tank carried a total of 40 shells with 8 armour-piercing and 32 HE projectiles. The protection was not the most important aspect, but it received enough armour to stop artillery fragments, 14.5 mm shots from 100 m, and it was protected against radioactive and nuclear fallout. While the tank was much superior to the PT-76B, it never went into service, it was deemed too complex to operate and produce en masse, so it was discarded and the PT-76 remained in service instead.

The Object 906 doesn't straymuch from the PT-76B, as it is pretty much an upgraded version of it, equipped with the already-mentioned 85mm D-5S cannon & featuring an acceptable wide range of shells to use for this tier, from APHE, HEAT-FS, and HE, all autoloaded.

For armor, it's a barely noticeable difference, now being able to survive heavy-caliber machine guns from medium to long range, but still very lacking, especially from the sides.

The only real special thing about this vehicle is its ability to swim, which is also shared with its predecessor.