The US Congress is questioning a Smithsonian deal that brought the museum four Stradivarius violins for $50 million. “The high-profile gift, one of the museum’s largest ever, allowed its donor, Herbert R. Axelrod, a New Jersey businessman, to claim what his lawyer confirmed was a tax break of around $32 million. Mr. Axelrod fled to Cuba in March after being indicted on unrelated charges of tax evasion.”