T-37

The T-37 was a prototype amphibious light tank based off of the T-27 and similar the T-41. The T-37 led to the development of the T-37A, which was the first mass-produced amphibious light tank in the world.

The T-37 was developed at the Leningrad OKMO, at the same time the 2nd VATO plant was producing the T-41.

It shared the same GAZ-AA engine as the T-41, and while the T-41 was produced in small numbers for the red army, the T-37 never saw production because of the incomplete development process and unsatisfactory steel casting quality.

Image Sources
http://worldwar2headquarters.com/HTML/tanks/RussianTanks/t37.html