CONCORD, N.H. — Federal agents in New Hampshire have made it possible for an auction house to sell a gun that was strapped to Bonnie Parker’s thigh when she and Clyde Barrow were ambushed and killed by law enforcement officers in 1934.

Amherst-based RR Auction obtained the revolver from a private collector this summer and noticed the serial numbers had been obliterated. The auctioneers contacted the Manchester office of the U.S. Alcohol, Tobacco, Firearms and Explosives.

Agents there confirmed the .38 caliber Colt Detectives Special had a serial number when manufactured, making it illegal to sell without one under the federal Gun Control Act of 1968.

The agents then secured an ATF-issued serial number for the gun — which was stamped on the gun’s receiver. That made it eligible for the Sept. 30 auction in Nashua.

“ATF understands the importance of this historically significant firearm,” said Guy N. Thomas, special agent in charge of the ATF Boston Field Division. “We are pleased we were able to work in partnership with RR Auction to make the gun legally compliant.”

The notorious Bonnie and Clyde were killed in a fusillade of police bullets on a Louisiana back road, after a two-year robbery-and-killing spree.

The gun is being auctioned off as part of RR Auction’s “American Gangsters, Outlaws and Lawmen” live auction at the Nashua Crowne Plaza. The auction also features a signed deposition by Al Capone dated Jan. 24, 1925.

The deposition is part of a 50-page archive of police interviews and notes on the investigation into the attempted murder of Capone’s mentor, John Torrio.

The gun and deposition are among more than 130 items featured in the auction. There’s also a vintage press ID card autographed by legendary lawman Eliot Ness from the 1930s, after Ness left Chicago for Cleveland to serve as director of Public Safety.

RR Auction is donating the proceeds of a September 28 open house to the National Law Enforcement Officers Memorial Fund.