Originally Posted by T-Mar

The helical ridges can be easily seen in the 3rd photo of the OP's original post. So, the fork is definitely at least SL.

The odd features of the bicycle are the long rear dropouts and eyelets. None of the bicycles in the referenced catalog (which is actually from 1982) have these features, nor do any in the 1985 catalog. This seems contradictory to other features, such as dual water bottle bosses and pump peg, which would date it post 1983 based on the catalogue. Of, course, these feature could have been added. However, in 1984 (and possibly 1983) Pinarello marketed a full Columbus SL model called the Gran Turismo. This model seems to have been intended as a fast,one day tourer, as it used the standard racing geometry except for a 20 mm longer wheelbase. This would explain the long dropouts and eyelets. It also had dual bottle bosses and a pump peg and would have featured modern style embossing. Pending further evidence, a 1983/1984 Gran Turismo would appear to be the best candidate, as it explains the era contradictory features.