I got this secondhand years ago, so I’m not sure who modded it but I don’t believe it was Keeley (otherwise they probably would’ve added their sticker to the back) but it’s the same type of mod. That additional switch when activated to the left adds a boost of low end heft that the original BD-2 cuts from your signal. To the right the switch returns to the stock Blues Driver sound.
There’s some scratches and dings as all used Boss pedals have but it’s in otherwise great shape and everything works perfectly.