In 1991, Nintendo used special cartridges for its Campus Challenge and later destroyed all but one; the survivor reached a New York garage sale in 2006 and resold on eBay for $20,100 three years later

• It looked like an odd old Nintendo cartridge sitting among boxes of gaming memorabilia.
• But when video-game collector Rob Walters came across it at a New York garage sale in 2006, he had stumbled upon something that Nintendo had never intended to become a collector's treasure.
• The cartridge was made specifically for Nintendo's 1991 Campus Challenge, a nationwide gaming competition that took place at around 60 US college campuses and other locations.