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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.
Feel free to quote small parts of the information on this page, but copyright law requires be listed as the source of the information.
In this website, we credit the people involved in the understanding of these codes. (Naturally, for information provided by others, such as for the Campagnolo and Williams codes, the original source should be cited.)Ben writes: "Brakes and brake levers often have date codes on them.
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).
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.
Weinmann and Dia-Compe calipers usually have codes on the back of a caliper arm.
This can be simple like "0784" (month 07, 1984) or a clock-type, with year in the middle and a ring of numbers with a tickmark pointing to the month.""Dia-Compe road levers usually have a code stamped _inside_ the lever.
The rear derailleur freewheel/cassette and chainwheels are probably the first to be changed on a bike.
On a vintage bike in excellent condition (that apparently had a lonely existence in a garage) all of the components likely are original.
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.