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.
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.
Even those equipped with Suntour Superbe components usually had SR seatposts.
Many components are marked with size descriptors in addition to component manufacturer's date codes.
This makes dating the components an interesting archeological investigation, but one not necessarily related to the date of the bike. Trek owner Larry Osborn made this observation, and suggested this as a supplementary way of dating a Trek (and other bikes as well).
Fueled by this first realization, and with the help of other bike folks, Larry and I have sorted out other codes (a project still ongoing).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.[Atom] [Brooks] [Campagnolo] [Dia-Compe and Weinmann] [Huret] [Maillard] [Normandy] [Nitto] [SR (Sakae)] [Sachs-Huret] [Shimano] [Strong] [Sansin] [Sunshine] [Sun Tour (Maeda)] [Sugino] [Tange] [Williams] [Dancing Chain] [Saddles]The date of manufacture of a bicycle's components can often be used to determine the date of manufacture of the bike itself.