Looks like a Montello,
The absence of a chain stay bridge is one sign it is, but I cannot get a good view of the top of the bottom bracket she'll from your pics. A Montello would have two reinforcing triangles on top of the BB she'll with the Pinarello "GTP" symbol cast on it.
Value will depend on the condition of the finish, and chrome, mostly. Some will pay quite a bit more if in some way, the notoriously fragile decals the Pinarellos came with, had survived in perfect condition. With what I could see in the pics, as is, I think it could sell for as much as 500 bucks. If the paint and chrome cleans up to near new condition, you might be able to add another 200 bucks in a hot market. In mint condition with pristine, original decals, maybe up to 700 bucks. Find two really aggressive Pinarello collectors to bid against each other, add another 100 to 200 bucks to that.