Originally Posted by T-Mar

I really don't think this is a later Treviso or whatever. The critical details are the Campagnolo dropouts and lack of a pump peg. The bridgeless Treviso use the later Pinarello branded dropouts and have a pump peg. I'm not sure exactly when the Pinarello dropouts were first used, but they were in place by 1989 and the Treviso still used a chainstay bridge that year. Pump pegs where in place by 1986. So, the OP's bicycle should be pre-1986. The OP's bicycle also does not appear to have a second set of bottle bosses and, if true, that would further corroborate the era.

The only other Pinarello that I'm aware of from pre-1985 that used the internal brake cable routing are the ARCO LA84, Prestige S and Tre Cime. The ARCO LA84 definitely did not use the bridgeless bottom bracket shell and had the easily recognized, oval SL tubing, so it's definitely ruled out. I'm not sure if the Prestige S and Tre Cime had the bridgeless bottom bracket shell, but I doubt it, as it's not mentioned in the catalogs, yet it was a highlighted feature in all the catalogs featuring the Montello.

So what does the OP have? It could be a factory error. Somebody grabbed the wrong tubes (I'd still want the OP to feel inside the down tube, chain stays and calibrate his finger on the steerer, just to be sure). It could also be custom. Finally, it could be a spec unique to the distributor/importer, if it's a non-USA market frameset.