I believe it's a Fiat 2800 also known as Camionetta CVP4, the design was obviously strongly inspired by the "carriers", you can actually seen the front end of a war booty carrier dehind the mock up.
You were on the wright tracks (no pun intended) before yes indeed it is the Fiat Cingoletta 2800, It was a obvious copy of the British universal carrier but bore more ressemblance to the American version the US T-16, It mounted a 8mm MG and with a load of 1 ton could still reach 60 Kph, Sorry spotter nearly but not quite there Your go TOS
It is very early but not Italian or French HINT: AFAIK it's the first tank from it's country with a 360 degs revolving turret.
Much smaller than the Neubaufahrzeug, and I already said it's not German, and not US. HINT2: that pic is seen from the rear, the tank is a turretted rhomboid that was not selected for mass production.
AFAIK the mark VIII never had a turret, but you are getting closer. BIG HINT: The following model, that did away with the rhomboid configuration, was mass produced.