Warwick Rockbass Steamer Standard knobs

Well i just got this bass used, and no manual unfortunentally, but i do want to know what each one of the knobs do! I've played with them, but can't really tell what each one does.. There are three, and i don't think one is volume.
Btw its a passive bass, just thought that might help to those who are trying to guess.

So anyone want to help out a 'wick nub?

Thanks

~craig