hmmm, early frame for sure and with that BB shell: Torresini made (perhaps)? Unsure about if legit 531 but it's certainly not out of the question (other Italian builders used it, but not "many"). The lug cut-outs and details don't look super well-finished but would not surprise me if this might be one of the very first contract-built "authorized" frames to cash in on Beppe's fame, before Colnago got into that (bigger-time).
Then again, could be a "fake" re-decaled. Those are Modolo mid-grade calipers I have not heard of before ("Speedy" yes but not "Sporting") and not that saddle before either but looks like a variation on the San Marco "Rolls".
Last edited by unworthy1; 10-03-20 at 11:20 AM.