Personally, I never use weight in an attempt to determine tubesets. There's such a variation in the weights of lugs, BB shells and other fittings, especially when you consider how much some manufacturers pare them.

Having said that, it is a very light frame. To the best of my knowledge, KL did use the patented steerer with helical reinforcements. KL used a traditional single butted seat tube but with a 0.1mm thinner wall than SL, so you nay be able to discern the difference via seat post diameters. Are you sure it's Columbus?