This clearly is when the component was made and not when the bike was made, but unless the component or bike manufacturer had lots of stock lying around in inventory, the date should be a fairly good indication of the year of the bike.At least it would be the earliest date that the bike could have been made.
As the wear on a vintage bike increases, the greater the likelihood components are not original, either through replacement of worn parts or through component swaps.
Swaps can take place early in the life of a bike as the proud new owner upgrades to new or used components of higher quality.
Swaps also can be made as the bike falls out of favor, or is being sold, where the higher quality components are traded for lower quality ones that the owner had onhand.
(Don't all cyclists have boxes and boxes of old components in their garage?
Pull the lever and look inside the top of the lever arm for a code such as "1084." Dia-Compe extension levers (yuck) also tend to have date codes on the side that faces the brake hood.
I have a set of Dia-Compe mountain levers where if you pull the lever all the way, a piece of the lever is exposed, which has a clock-type date code.Unfortunately, many of these are coded, and require some additional knowledge to understand the code.If you know of other components that are marked or coded that can be added to this list, please let me know.: The information on this page is copyrighted.For example, the back of cranks are usually marked with crank arm length in mm, typically in the range of 165 to 185.Seatposts are marked with outside diameter, also in mm.Even those equipped with Suntour Superbe components usually had SR seatposts.