HARTFORD, Conn. (AP) — A reputed mobster who authorities believe is the last surviving person of interest in the largest art heist in history is facing sentencing in an unrelated weapons case.

Eighty-one-year-old Robert Gentile is set to be sentenced Tuesday in federal court in Hartford, Connecticut.

Federal prosecutors have said they believe the Manchester resident has information about the still-unsolved 1990 heist at the Isabella Stewart Gardner Museum in Boston. Thieves stole an estimated $500 million worth of artwork, including works by Rembrandt and Johannes Vermeer.

Gentile has denied knowing anything about the caper.

Gentile pleaded guilty in the weapons case and faces three to six years in prison. Authorities say they seized firearms and ammunition from his home that he was not supposed to possess because he is a convicted felon.