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.Of course, all this assumes the bike has the original component.The most likely components to be original are the stem, handlebars, seatpost, and brakes.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.[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.Some bike parts have a date code cast or stamped into the piece.
Following Ben's lead - I checked three sets of Dia-Compe G calipers and all have the four-digit date code on the back of one of the arms.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.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.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.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.