Wheel/Track

Following WW1 and a side trip to deliver the "M-21" to Sweden, Josef Vollmer, the former chief designer for the German War Department's motor vehicle section, came to reside in Czechoslovakia. Joining Skoda, he set to work on a wheel/track light tank. His KH-50 design had roadwheels mounted on the drive sprockets and a jockey wheel behind to keep the tracks up off the ground.
Despite impressive specifications - 13mm armor, a 37mm turret mounted gun, and a 50hp engine capable of pushing the tank up to 8mph (tracks) and 22mph (wheels), it was rejected by the Czechoslovak army. However, the army was impressed. The military liked the hybrid Kolohousenka wheel/track arrangement and commissioned further studies. Further designs would be the KH-60 and 70.
Notable differences would be the engine power increased to 60-70hp and a better system of switching between track and wheel. A simple ramp device allowed the track-to-wheel change in less than 10 minutes.
The actual years of production and testing were 1925 - 30, during which time, two KH-50 prototypes were built. One was rebuilt into a KH-60 and the other scrapped. Actual production included two KH-60 for the USSR and one KH-70 for Italy.
As time passed, this vehicle came to be regarded as more of an experiment rather than a combat vehicle.

Source: TANKS!