Okay, I've found a lot of crazy stuff on craigslist, but this one confounds me. First, the craigslist ad:

"touring 10speed

10 speed lemans,quick release,531 tubing etc,good brakes, 35$."

I'm the first caller and the owner says that I probably won't want it because the tires are flat. Anyway, I get down to the trailer park and find the bike, which is actually a Centurion Le Mans 12. Here's where it gets strange: the bike looks awful. It has goofy stickers all over, rust spots covered in nail polish, and duct tape holding the cable housing to the frame. Yet it has beautiful 600 cranks, dura ace downtube shifters and derailures and brand new continental tires! Now, I'm no expert, but I don't think the Le Mans ever came with that group, and I know that the previous owner didn't put them on . . . or did he? In the ad he mentions 531 tubing but nowhere on the bike does it say 531. Somehow he must have known that 531 tubing was a good thing, so why didn't he mention the dura ace stuff? Any ideas? Your first though might be that it was stolen, but I've bought enough craigslist bikes to know when a person is a thief and this was an old guy with a road bike, and maybe thats all it was.