From this Compusa flyer you can see the 49.99$ dvd burner deal (after 30$ rebate).
Reading the fine prints, the #314998 item is this.
MD-16XDVD9 is a rebaddged 3500, and MD-16XDVD9A2 is 3520, right?
However, its spec says 8x +rw, closer to 3520. Maybe they're just too lazy to change its name.
Anyway, it's not a bad deal for 3520, and if it is 3500, maybe this is your last chance to buy one.