The gangster hid the small pistol in a sock and it was found during his arrest in Tucson in 1934. Heritage Auction Galleries Director of Militaria Dennis Lowe described the pistol as a Remington .41 caliber Double Derringer. He said it was confiscated when Dillinger and some of his gang were arrested in January 1934 -- six months before Dillinger was gunned down in Chicago.
The gallery estimated the selling price will be about $35,000 when the weapon is auctioned July 25.
The name of the consignor was not released, but a press release from the gallery described him as a "member of a prominent Tucson family." The release said he owned the gun for 50 years and decided to sell because he is in failing health.
Dillinger is the subject of the current U.S box-officer release, "Public Enemies," starring Johnny Depp as Dillinger.