The need for a more powerful armoured vehicle - the tankettes being incapable of an actual combat role - forced Poland to turn her attention to a further Vickers product, namely the Vickers-Armstrong Six-ton tank, (Vickers Mark 'E'), which was soon to gain a worldwide reputation for a whole decade. In fact, between 1930 and 1939, Vickers-Armstrong Ltd sold over 190 machines of that type (tanks and tractors) to foreign countries - Bolivia, Bulgaria, China, Finland, Greece, Japan, Portugal, Russia and Thailand (Siam) - but the largest order came from Poland with a total of 50 (other sources give 38) tanks with either the single and twin turret arrangement.
The fact that the Vickers-Armstrong Six-ton tank was well within the capacity of the Polish technology, and as it offered some potential for further development, the PZI design bureau was entrusted with the study of a homemade copy. Subsequently PZI produced the 7 TP, a 9ton twin turreted tank which was to be a considerable step forward in design over the Vickers original. At first, the Armstrong-Siddeley engine of the Six-ton was replaced by a licence-built Saurer 6-cylinder diesel engine which developed 110hp, so making the Polish 7 TP the first diesel-powered tank to reach production status.
The 7 TP armour was also 4mm thicker than the Six-ton armour. The first 7 TP to be built by PZI left the works in I934 and production continued at a slow tempo up to 1939. While the production of the modified twin turret model 7 TP was proceeding slowly, it was decided to introduce a single version carrying a Bofors gun (the turret being manufactured by this same concern). This variant appeared in 1937, but the production was restricted by the difficulties of making armour plates and of procuring the turrets from Sweden. Afterwards, in 1939, some quibbles about its unsuitable armour thickness brought PZI to evolve a heavier variant with an improved engine, welded armour thickened up to 40mm in front, a strengthened suspension, wider tracks and a turret with a rear overhang which could accommodate both transmitter and receiver radio sets. The up-armoured 7 TP, which now weighed 11 tons, did not have time to go beyond the prototype or, at best, pre-production stage.