3-Way Split (1976)

Tony Pintana, an art collector, and his wife are contacted by Martin, who is short on cash and proposes to rob a museum of a Indian golden mask that's worth 10 million dollar. When their attempt miserably fails, the museum decides to have the mask transported to a safer location. The three try their luck again and are successful this time. Chased by a policeman who isn't convinced they're innocent, the three will have a difficult time selling the mask on the black market.