At least half the people selling bikes out there don't really have any idea what the hell they are selling. "Nice Old Bike - $50" (no picture) is, in my neck of the woods, a very common CL ad. I've called (and in some cases, bought bikes from) people who couldn't be bothered to take note of the various labels on their bikes. On the upside, these people are just as likely to take $30 for whatever it is they have.

Sometimes it's a Centurion Iron Man, sometimes its a cast iron Huffy. (In which case you can politely tell them their bike is worth more like $20, and drive the point home by declining to buy it at that price.)