Same seller I purchased from. It works fine. Despite my initial impressions, after opening the device it seems it is a counterfeit or a hand-fixed throwaway. Quality seems good but the soldering is poor in places.
For the price, not a terrible deal--I may have haggled with the seller if I knew it was fake. I notice now that they sell deliberate "clones" in black enclosures, which are probably the exact same boards in a different housing. Would probably go for one of those. I don't think I could convince myself to pay >$500 for a "real" one in any case.
So I don't know, I'm not thrilled I was duped. I found references on the time-nuts mailing list originally that claimed these units were authentic surplus Agilent products. I searched eBay for the most reputable-seeming seller and took the risk. Exterior-wise, my unit looks very, very convincing. The plastic housing feels high-quality, the cabling is high quality, the cable strap around the cable is high quality. Came in very convincing packaging. The GPIB screw anchors look exactly like those on my authentic, Agilent-purchased GPIB cables (hard to describe, the sort of stippling on the metal surface).
Only after opening the case did I realize something was up. That the warranty was "expired" didn't alarm me, as I was under the impression these were old units anyways.
So I don't know. My ego is hurt more than anything, as the device still works fine. I mainly feel bad that I said the item was genuine, when clearly I was not the best judge of that fact. I have edited my original post, so others aren't misled by my naïveté.