OK...here's the deal...
The FIRST day is a large swap at the Velodrome...it's a very fun time. There are vintage bikes, newer bikes, shops selling last year's stuff cheap...you name it. Sellers range from racer's selling their old frame because their team just gave them a new one to C/R list guys selling 531. The vintage stuff is more along the lines of CR list vintage...60s - 80s lightweights. There are other things, but that's what predominates.
The SECOND day is at the nearby firehouse and it consists more of the weirder, older stuff...though it has lightweight CR stuff as well. Cruisers, krates, Boneshakers...etc.
If you can, go both days

I haven't done that in a while, but it's awfully fun to do. I actually haven't gone at all in a few years but it looks like I will go this year.