May I make a suggestion about the turret?
Turrets are complex pieces of equipment since they use a ring gear which is an expensive machining job and requires specialised machine tools. My thought is that the creators of this tank might well have reused the existing turret machinery of a tank in production and possibly used the castings of an existing turret as well. About the only tank in production in Spain at this time was the Trubia Naval which had a turret somewhat like the Barbastro design - as far as can be deduced from the images. There is a 1:50 model of the Trubia Naval around (see edit) which might help.
Charlie
Memory finally produced the goods - it's a Robototehnik model -
https://vk.com/robototehnikpaper?z=p...01381877%2Frev