The overwhelming majority of Mercians sold in the U.S. came into the country as framesets. My ride quality experience has been very different from onyerleft's . My '02 Mercian Vincitore custom road fixed-gear (classical British club bike geometry with track ends for fixed gear use, clearance for mudguards, etc) has cheerfully handled every road surface from buttery asphalt to neglected chipseal to gravel and hardpacked clay. My '82 Colorado that started life as a team-issued racebike blends stability and nimbleness and responsiveness in ways much costlier customs didn't.

Much depends on the tubing used, too. The Colorado is 531c with round section 531 forks and round stays with a good bit of taper to them, while the Vincitore is 531c with a 531ST fork.

The serial number will give you a year of production, but somewhere along the line they changed the format. My Colorado is 45882 with a 6 that indicates it was built by George Bryan, while the Vincitore has a three line number; 5 for builder Derek Land, 181 for the number built that year, and 2002 for the year built.