What's a Bias torque slipper? is it a limited slip diff?
It certainly could indicate he at least thinks it's an LSD, but using terminology like that, I'd be worried he doesn't have a clue what he's talking about, and would be wanting confirmation it's an LSD, eg in the form of a photo of the innards, before considering bidding.
Ive got a LSD the same as that lying here...
Looks like a standard Sierra lsd to me.
It has a standard viscous diff apparently, so absolutely nothing to do with a torque biasing diff. Clueless eBay user.