I've never seen this design before. Since the Italian troops fighting in the Francoist side during the Spanish Civil War were nominally volunteers (their name was Corpo Truppe Volontarie), their flags did not always follow the Italian official patterns, and thus a flag like this one could have been used, but, as I said, I don't remember having seen this kind of design in any of my sources. Anyway, the central emblem is rather odd: it combines the Fascist
fasces with the Falangist yoke and arrows, but, surprisingly, there are two yokes instead of one (and I'm not 'yoking'

)
The problem with this kind of objects is that generally there are no documents to back what the seller says, and then you have to believe him or not.