The face of Mary, Queen of Scots

Studies of a dab of yellow pigment and the ancient wooden background of a painting once attributed to an 18th century artist have revealed the work is a rare contemporary portrait of the fiery, redheaded Mary, Queen of Scots.

The 16th century oil measuring 10 inches by 7 1/2 inches is considered the only portrait made of Mary as queen, said Catherine Bromley, spokeswoman for the National Portrait Gallery in London, which has owned the painting for nearly a century. Only two were painted in Mary’s lifetime.

The painting shows Mary in an embroidered black coat with high white ruffled Tudor collar and a flat black cap with pearls and a feather of the kind more usually worn by men. The artist is unknown.

The gallery is not saying how much the painting -- bought at auction in 1916 for what was then $238 -- is currently worth.

Covered in unsightly yellow varnish, the piece had been written off for years as an 18th century fake and was not displayed.