What is the BB thread? It's easy to tell if it's Italian by trying an Italian cup. If it seems even in the ballpark for threading in, then it's Italian. French, English and Swiss are a full mm smaller, so there's no mistaking the fact they won't begin to fit. Conversely if you check it with say an Eng cup, it will fall in without the threads touching.

I agree the frame is unlikely to be an Italian make, what with the French-made (Prugnat) fork crown. Back then it was rare for an Ital builder to use French frame parts. Even if the BB thread is Ital, I'd still be skeptical. That'd make me think USA, since a few US builders used Ital BBs.

Yes those dropouts are Italian-made but almost no Ital builders used them.

Yes Cinelli used seatstays that attached with the seatpost pinchbolt integrated into the stay tops, but not like how it's done here. The cylindrical boss with the stays mitered to it is mostly Eng. or US. Never seen an Italian do that, counterexamples please if you know of any.

It's an intrguing frame, whatever it is. Keep us posted if you find more info on it.