To muddy the water even further, I've found a picture of a known 1988, Canadian market Montello. It looks very much like the US models. The fork, chain stays and seat stays are full chrome. It has the Pinarello logo on both sides of the seat tube. It has a pump peg. The chainstay cable stop is in the traditional, forward position. I can't tell if it has two sets of bottle bosses or the style of head emblem. However, it probably has two sets of bottle bosses, as they seem to have gone to the logo on both sides of the seat tube at the same time they went to two sets of bosses, probably so that a 2nd bottle wouldn't oscure the single logo, on the front of the seat tube.

So, the OP's bicycle, despite have most of the attributes of an earlier model, is still puzzling by virtue of the rearward mounted, chain stay cable stop and the Columbus decal.