Difficult to tell from the photos, but basically the rule is if it has Gilco tubing then it's a master of some sort, if it has crimped tubing then it's likely to be a Nuovo Mexico.
However, rules are made to be broken and nobody broke them more often than Colnago.
If I really, really, had to make a guess, I'd go for it being a Master, certainly the teardrop shaped cutouts in the head lugs point that way.