They're not from Backblaze, the rep that frequents /r/DataHoarder said they destroy their drives when someone asked them about these coming from them.Sounds like these are all from Backblaze.
I also want to update, I finally went through and scanned the 20 drives I got from the $30 sale. I used HD Sentinel to test them all, and first just went through and checked their SMART stats. 18 of them were clean w/o reallocated sectors and very low start/stop times but about 3 years of online time, which is about what I expected for the good, used ones. The other 2 had a high number of re-allocated sectors but weren't dead, however the software has their estimated time to live at weeks so they're gonna go back.
Then I took the 18 good ones and ran read and write surface tests on each one. Took about 3 days since I can run 3 at a time at 8 hrs a piece in my SATA hotswap cage and run a set while I sleep and a set while I am at work. 16 of them passed with no extra bad sectors. One of the two others reallocated 1 bad sector, which I find acceptable. The other one reallocated 18 so the software put its health at 36% so I might send that one back with the other two.
So, 17 good drives - 16 perfect for $600. Total of 32TB. I think that's a pretty damn good deal.