The fine vertical scratches on some were from using an HP6520 to feed and scan a pile of prints automatically. They were fed over a strip of glass around 5mm wide. However, a piece of paper dust on the glass from the prints caused the multiple fine scratches seen on some of the scans. Scan it again, you got different scratches, as seen here (It's what I sent to HP)

As the images say on Flickr, I returned 3 printers before giving up!
On with the topic......

























