Brian Anthony D’Ambrosio pleaded guilty in federal court on July 9 to theft of major artwork.

The New Mexico man, 49, is accused of stealing 100-year-old items, including letters by the wife of Western artist Charlie M. Russell from the Montana Historical Society and selling them for profit on eBay, according to the U.S. Attorney’s office.

D’Ambrosio faces a maximum of 10 years in prison, a $250,000 fine and three years of supervised release.

Chief U.S. District Judge Brian M. Morris presided.

The court will determine any sentence after considering the U.S. Sentencing Guidelines and other statutory factors.

Sentencing is set for Nov. 13 and D’Ambrosio was released pending further proceedings, according to the U.S. Attorney’s office.

D’Ambrosio allegedly claimed to conduct research at the Montana Historical Society in Helena and stole items from the archive from about April 2022 to September 2023, according to court documents.

Stolen items included letters written by Nancy Russell, were more than 100 years old, of cultural heritage and exceeded $5,000 in value, according to court documents.

D’Ambrosio then sold and attempted to sell the stolen items for profit on eBay, according to court documents.

An undercover FBI agent posed as a would-be purchaser to confirm D’Ambrosio was the individual stealing the items and selling or attempting to sell the items on eBay for a profit, none of which was authorized, according to court documents.

D’Ambrosio, an author on Montana subjects, was initially also charged with interstate transportation of stolen property and wire fraud, but those changes were dropped in a plea deal in which he agreed to plead guilty to art theft.

The U.S. Attorney’s Office is prosecuting the case. The FBI and Helena Police Department conducted the investigation.