[CharlieC]

They might have used or copied tracks from existing armoured vehicles being made in Spain at the time. The city of Barbastro is about midway between Bilbao and Barcelona where the Trubia Naval tank and Benach Armoured (thing) were being built. The Trubia track was, I think, a modified Orion track system but the Benach track looks like a fairly generic track of the period. There's even a surviving Benach OP tractor (base for the armoured things) in Spain.

Charlie