Thanks for the info guys. I've already been looking at a few similar parts on mouser and digikey, but for the same specs (pretending for a moment the ebay chip was the real deal) they're almost 10x more expensive, which is why I checked on ebay.
I'd expect the occasional seller mis-describing or mis-labeling a part, but the thing is that there are dozens of sellers, all claiming this to be an ADC.
Now, as far as buying this on ebay in china. You have to be bonkers. Go to mouser or digikey
Because you never know!
Example: I've found some lovely little SOIC8 16-bit DACs for 50 cents a pop on ebay, the PT8211, and they can't really be found in any of the big stores (except futurlec, which I tend to avoid). They work, been using them for years, so I hoped I'd be just as lucky for ADCs.
The difference is of course that info on the 8211 CAN be found.