10TP Tank

The 10TP was a Polish light cruiser tank prototype. It was designed back in 1935 by a team of engineers leaded by Major Rudolf Gundlach as "natural" development of the previous 7TP light tank.
By 1936, even if the design wasn't complete, it was approved to be included in the programme of armoured forces that was part of a bigger plan to modernize and expand the Polish Army during the period of 1936-1942. This tank was expected to be part of the tank battalions for the newly created motorised units.
The prototype was started to be built in 1937 at the State Engineering Plants, located at the outskirts of Warsaw, where every Polish tank during the period of 1931-1939 was manufactured. At the same time, two motorised cavalry brigades were raised, in order to be equipped with this tank.
It was completed on 16th August 1938 and its trials were kept in secret as the activities of the German Abwehr were becoming more intensive. In January 1939 it was further tested and it managed to travel a distance of 610km (379 milles). Before it could be massly produced, Poland was invaded by Germany in September 1939 and any further development was halted.

Sources:
1. https://en.wikipedia.org/wiki/10TP
2. Salamander Books - The Illustrated Encyclopedia of the World's Tanks and AFVs.