I just realized that my old Playstation controllers do not have "Dual Shock 2" inscribed on it. so I would think it's safe to assume that I have PS1 controllers. What I'm curious to know, can they still be used with the PS3 via the USB adapter?
PS1 controller should work with the USB, but I can't confirm. Even if it works, you won't be able to play most PS2 games. I remember a lot of games wouldn't work with standard PS1 controllers, even if there were the 2 sticks. This apply too for Sony's PS1 controllers.