Originally Posted by rustystrings61

For pre-1970 bikes, there's this site, which is mostly photos linked to serial numbers. Mercian has serial numbers for bikes built from 1970 on, but they charge for looking them up now after years of people having them stop what they're doing to poke through files. What I posted before seems to be largely correct - the last two digits of the long number are the year of production. To my knowledge, no one outside Mercian has posted a listing of the builder's numbers, which I would imagine would change over the years.