LONDON (Reuters) - A unique portrait by Italian Old Master Titian, painted over and rediscovered more than 400 years later, is expected to make more than 9 million dollars when it is sold at auction in December. Revealed by X-rays and painstakingly restored, Titian's Portrait of a Lady and her Daughter was unfinished when the Renaissance master died in 1576 and painted over with Tobias and the Angel, probably by one of Titian's pupils, Leonardo Corona. "It is a singularly beautiful picture. There is an intimacy in the relationship between the mother and daughter. There is no doubt about that,"...