An 18th-century British painting stolen by mobsters in 1969 has been returned more than a half-century later to the family that bought the painting during the Great Depression. “The Schoolmistress” by John Opie is the sister painting of a similar work housed in the Tate Britain art gallery in London. The FBI’s Salt Lake City field office announced that it was returned to the son of a New Jersey doctor who originally bought it for $7,500.