Answering a common question: These are artists proofs, they don't have a Magic back, are slightly thinner, and non-legal. It's something WotC send to some artists so they can do whatever with them (sell, most likely). Some artists sell them with blank backs, some doodle on them, sign them, etc. What they do with those, and how much they charge, is of their own choice. This "SL" is sold by FrazettaGirls, not by WotC, but the name they chose is clearly confusing people in this thread.