IMHO Montellos don't really fit into this discussion as they are so different than the middle to "lower" end, with SLX, and unique BB shell.
The mystery Pinarello in my possession has the flush bottle mounts on the seat tube and standard braze on bottle mounts on the down tube.
P1030827 on Flickr
The post diameter is 27.2. Plain seat stay caps but GPT on the brazed on FD mount. Clearly Pinarello BB shell and no chrome anywhere. The fork is sloping with no markings. I know it is original because the original paint was on the bike when purchased and the steerer was marked with a dove and overspray. DO are Pinarello. Stripped Painted frame was 4lb 10 oz with the fork coming in at 1lb 12oz. Bike as purchased was 22lbs. SN 178 C.

Pinarello Vento- as purchased on Flickr

At first I thought it was a Tre Crimi but it doesn't have the chrome chain stay. I ended up believing it is a Veneto. Paint was so bad, I stripped it. Built it up with Suntour Superbe for my daughter (too small for me) and she loved it. Need to finish it. I think it will get 105 group set.

Pinarello Veneto on Flickr