I recently came across some eBay auctions which alluded to the fact that the Columbus tubing decal varied slightly through the 70's and thought that might be a good way to narrow down the year of a bike from that decade. Here's a first go at the it. Comments, corrections, and suggestions much welcomed.

Below is a work-in-progress of a possible timeline for Columbus decals. Scroll to bottom of page for some of the tubing names / descriptions.

	1965?
	1960s?
	1969-ish
	1970-ish
	1971 to 1972
	1972 to 1974
	1973 to 1975
	1975 to 1978
	1978-ish
	1978 and after

John J.:

In the mid 70's there was:

KL the stupid light stuff aka Record tubing
SP heavy strada
PS sprint heavy stuff 24mm blades, also avail with the collared down chainstays 24mm reduced to 22 at the BB sockets
PL the light pista stuff 22mm blades
SL the light road stuff, I think .9/.6/.9

plus the variations of  seat stay diameters and tapers, crimped or no crimped chainstays etc.

In the 60's it was shape that was a guide to the tubing type.

John T.:

Columbus didn't distinguish between SL/SP during the on-topic era. The tubes themselves were marked with the wall thickness (e.g. 0.9/0.6 for an SL down tube) earlier with a stamp, later with graphite electrode.

The markings were often lost when the tubes were trimmed and/or covered with paint after brazing.

This is very interesting.  I've been trying to pin down when my Galmozzi, with its many period incorrect parts, was made.  Its crank is from '74 (diamond with "4" inside) and its saddle is from '73.  So, I gather from your timeline the frame was made a year or two earlier.  Any corrections to this timeline since you originally created it?

gridplan:

This is very interesting.  I've been trying to pin down when my Galmozzi, with its many period incorrect parts, was made.  Its crank is from '74 (diamond with "4" inside) and its saddle is from '73.  So, I gather from your timeline the frame was made a year or two earlier.  Any corrections to this timeline since you originally created it?

Neat bike.

Dating frames by the Columbus decals can be useful as an additional datapoint. However, it seems builders sometimes had inventory that they didn't always use up right away and so the potential for older decals to be used on later frames is a real possibility.

IMHO, it would be very difficult to pin down a year for bikes like your Galmozzi without the original build order. :-(   When I approached Ernesto Colnago with my (Colnago-built) Molteni-Merckx even he made the mistake of dating the frame to 1970 when it obviously could not be that old due to his relationship with Eddy not yet being formed.