The two sets of Dia-Compe brake lever bodies I checked had the four-number date code stamped inside the lever body (I couldn't find any markings on the levers themselves).However, a Gran Compe set of calipers had no markings. For example, 1182 means the 11th week of the year 1982.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.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.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?
On a vintage bike in excellent condition (that apparently had a lonely existence in a garage) all of the components likely are original.
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.