Last year saw Nike raise $6.75 million for the Michael J. Fox Foundation through various raffles and auctions of the power-lacing Nike Mag. A year later, the original Nike Mag that Marty McFly wore in 1989's Back to the Future II is similarly set to hit the auction block. Spotted on display at this year's Comic-Con San Diego, the shoe is currently being held by the movie memorabilia specialists at Prop Store, and is expected to be auctioned off this fall. The shoe is expected to fetch winning bids ranging from $32,000 to $45,000.