The new readers are black, the old (unencrypted ones) are white. There was a presentation at BlackHat 2011 on how to use them as general purpose skimmers: http://www.engadget.com/2011/08/05/square-found-to-be-ripe-f...

The new readers are also white. Look very similar to the old ones but slightly thicker.

Well, I do own a black reader, so perhaps Square moved back to using white at some point. But there have been white readers unable to encrypt the data out 'in the wild', and I suspect this project used one of those.