In a half decent market, a full 531cs framed, cantilever equipped vintage Trek tourer should bring between 350-400. Offer me 250 and I'd laugh.
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My bikes: '81 Trek 957, '83 Trek 720, '85 Trek 500, '85 Trek 770, '81 Merckx, '85 Centurion Cinelli, '85 Raleigh Portage, '92 RB-2, '09 Bianchi