Got them today. They were just thrown in a box full of packing peanuts, so I'm going to email the seller and ask him to warranty the drives.
They show up as WD6000FSYZ (instead of WD6001) with firmware SP00 and serial numbers that show invalid on WD's site. They had 73 hours of use and adhesive residue where a small label was on the top. On the front side there's a small label with "DY5E 276". When powered up, they make a periodic seek noise as if they are doing background activity, which causes the seek times to spike.
I will be doing some extended burn in on these drives to see if they fail. For simple non-critical/replaceable file storage they should be fine, but I wouldn't trust them for anything important. At less than half the price of one with a label (link in an earlier post), they're a great deal.
EDIT: Seller responded and said he's sold "thousands" of drives and shipped them all with just packing peanuts, didn't even acknowledge my request for a warranty. I wouldn't recommend buying from this seller since he doesn't know how to properly package drives.