This thread got my attention and I started digging around. Here's a little piece from mtg news about these things:
http://www.mtgnews.com/F/Topic/1078455686053__Rare__Middle_Ages_Expansion_on_eBay.htmlEdit: Here is a description of Middle ages from an auction summary on ebay...
"Middle Ages is a set of 75 Magic card stickers created in summer 1994 by Marauder Graphics run by Fred "Rich" Ditzler. The stickers were designed to be stuck on the frontside of real Magic cards. The print run consisted of 1,000 sheets, for a total of 90,000 stickers. They were distributed in booster boxes of 30 booster packs which contained 8 random cards, mostly to stores in Pennsylvania, New Jersey, and Delaware.Wizards of the Coast issued a Cease and desist order and the cards were pulled. These are very rare items to find and would make a great addition to any Magic the gather collection.
The stickers were printed on two sheets: an uncommon sheet and a common sheet, each holding 45 images. Additionally, some cards appeared more than once which allowed a variety of rarities, with "U1" (a card printed once on the uncommon sheet) being the rarest and "C3" (a card printed three times on the common sheet) being the most common. The card distribution was further altered manually during packaging by removing some cards, thereby creating what Mr. Ditzler called "ungodly rares". Exactly which cards were affected in this manner is unknown. A complete list of rarities can be seen here:"
Ebay auctions