I have never worried a bit about date codes, but I do think it is pretty interesting to find a bicycle with almost all original components, such as my 1960 Capo. However, those of us who actually ride our vintage bikes inevitably make a few compromises in the interest of safety and reliability -- after 50 years of use, most aluminum rims or handlebar stems become suspect, and there is no way I am going to ride with 50-year old brake cables or pads.
I just saw Rabid's post, and I concur.
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"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069