Eighty years ago this summer, the world was introduced to the Marvel Comics universe with Marvel Comics No. 1. Now, the highest professionally graded copy of the 1939 book is up for auction through Heritage Auctions.

At the time of publication, the book had a bid of $762,500, but Heritage Auctions predicts a final bid of more than $1 million, which would make it the most-expensive Marvel comic ever sold in an auction.

This issue is rated a 9.4 out of 10 by the Certified Guaranty Company (CGC) for its condition, which is unusually high. (For reference, there is only one other 9.4 in CGC’s census for the top-six most-valuable golden age comics.)

A mailman in Uniontown, Pennsylvania, originally purchased this copy of Marvel Comics No. 1 (for 10 cents). At the time, he bought every No. 1 issue he could find of both comic books and magazines.

Collectors have until tomorrow to bid on this one-of-a-kind treasure.

Photos: Heritage Auctions