If you have purchased any Germany kiloware in the last decade, you will have more duplicates of certain stamps than you could ever use. Some large format, self-adhesive stamps are made in astounding numbers. One such stamp is the "Roter Sand" lighthouse coil of 2005. This stamp was issued in the amount of 505.5437 million.
I was looking through these "Roter Sand" duplicates a few weeks ago and found a few interesting printing varieties. I guess when half a billion of something is printed, some plate and ink problems are going to happen. One of the stamps has tiny blue specks covering the entire surface. These specks don't show up that well on the pic. Another has tiny black specks covering the entire stamp. The third has red orange bands on the lighthouse and a different blue for the sky, probably because the red color was too thin, or it was running out.
Here they are.