The seat stay caps (& the fork crown) are engraved "GP", not "PT". GP stands for Giovanni Pinarello, the founder of the company.

I'm thinking it's a 1991 or later, and I am basing this on the decal on the down tube, between the shifter and head tube that says, Campione Olimpico '84 (commemorating Alexi Grewal's 1984 Olympic Gold) & Campione del Mondo '90 (who won a World Championship on a Pinarello, I do not know)

The fork crown indicates (to me) that it's an early '80s model. By the mid-to-late '80s, I think that Pinarello had gone to a more sloped fork crown. But there's that darned decal....

This is a tough one.