MINNEAPOLIS -- It's considered the Holy Grail of comic books: Action Comics No. 1 from 1938, featuring the debut of Superman. And David Gonzales found one mixed in with old newspapers insulating a wall in a house he was renovating in a small town in Minnesota.

Gonzalez did some research that confirmed the comic was valuable, though not as much as it could have been. He got into a heated discussion with a relative about its value, and the back cover got ripped.

Because of the damage, New York-based online auctioneer ComicConnect.com graded the book a 1.5 on a 10-point scale. By comparison, an Action Comics No. 1 that was graded a 9 recently fetched $2.16 million.

Bidding on Gonzales' find was up to $127,000 as of Friday. Bidding closes June 11.