Playstation controller I saw at a thrift store?

[WizDawg]

I saw a Playstation controller at a thrift store today I've never seen before and was wondering if someone knows about it. It was shaped like a black box and had 2 red buttons on the top. One (I think) said select and the other one start. There were 3 arrows on it too. I know it was a playstation controller because of the connector. Also there was a 9 pin male connector on the side. Can someone enlighten me on what this is used for?

Thanks.

[Mr.FoodMonster]

Sounds like it might've been a control box for a dance pad. I bet it looked rather similar to this, as described http://www.gameasylum.us/muuncoboxfor.html
Usually, you hook that up to a metal dance pad that has a 9-pin on it, and you can swap them out for other types of connectors, PSX/2, USB or XBox. Now that they have all-in-one connectors, just a PSX one isn't really neccecary.