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

Gonzales did some research that confirmed the comic with a cover showing the Man of Steel holding a car over his head was valuable, though it's not worth as much as it could have been.

The book sat undisturbed in the ceiling of the house in Hoffman for more than 70 years. A few days after he found it, Gonzales said, he entered into a heated discussion with his wife's aunt about its value, and she wanted a cut of the money. He said he also grew irritated because every time she would turn a page, crumbs of paper would fall out.

Finally he said, he grabbed it and tossed it aside, accidentally tearing the back cover.

"I don't care about the money," he recalled telling her. "I don't care. It's my comic book. I can burn it if I want to."

Gonzales said his wife's aunt backed down when his wife warned her he was serious.

Partly because of the damage and partly because the book shows the effects of its long service as insulation, New York-based online auctioneer ComicConnect.com said it's graded 1.5 on a 10-point scale. By comparison, an Action Comics No. 1 that was graded a 9 recently fetched $2.16 million.

"Valuable comic books so often have almost magical -- and in many cases, ironic -- back-stories like this," said Vincent Zurzolo, co-owner of ComicConnect.

Bidding on Gonzales' find was up to $137,000 as of Friday. Bidding will close June 11. Gonzales said he figures he'll get about half the sale price after the auction site and the Florida comic dealer he originally took the book to receive their share.

Gonzales said he understands the ripped cover and other damage might have shaved $75,000 off the potential price. He said that doesn't bother him.

"I'm not a hungry person about money," he said, adding that he'd rather work for it.