Roy Precious - Antiques & Fine Art has dated this piece to the Before 1700 period.
Certainly the sitter does bear a resemblance to Elizabeth Butler as depicted by Lely in a three-quarter length portrait owned by the Chevening Trust.

ELIZABETH BUTLER, COUNTESS OF CHESTERFIELD (29 June 1640/1 – July 1665)
Lady Elizabeth was born at Kilkenny Castle, Kilkenny, Ireland on 29 June 1640, the eldest daughter of James Butler, 1st Duke of Ormonde and Lady Elizabeth Preston.

She married Philip Stanhope, Earl of Chesterfield some time before 25 September 1660. He was one of the lovers of the notorious Barbara Villiers, mistress of King Charles II of England. There were many at court who believed Barbara's first child, Anne, bore a strong resemblance to Chesterfield. His first wife was Lady Anne Percy, daughter of Algernon Percy, 10th Earl of Northumberland; however, she had died on 29 November 1654 without having produced surviving children.
Together Elizabeth and Chesterfield had one daughter, Lady Elizabeth Stanhope, later Countess of Strathmore, although the child's paternity was in doubt. According to Samuel Pepys, theirs was a marriage of convenience, but Chesterfield, despite his own past conduct with Barbara Villiers, became jealous when rumours spread that his wife was having affairs with both James Hamilton and James, Duke of York, with whom she is said to have been caught in flagrante. On the other hand, he describes Elizabeth as "a virtuous lady".
The Chevalier de Grammont, in his memoirs, says of Elizabeth that, "she had a most exquisite shape, though she was not very tall: her complexion was extremely fair, with all the expressive charms of a brunette: she had large blue eyes, very tempting and alluring: her manners were engaging: her wit lively and amusing; but her heart, ever open to tender sentiments, was neither scrupulous in point of constancy, nor nice in point of sincerity."
In May 1663, the couple went to live at Bretby in Derbyshire. It was around this time that their daughter, Elizabeth was born.
The Countess died in July 1665 shortly after her 25th birthday and was buried on 18 July 1665 at Wellingborough, Northamptonshire. It was rumoured that she had been poisoned by her jealous husband.
Her daughter, Lady Elizabeth (May 1663- 24 April 1723), who was a child of two years at the time of Elizabeth's death, later married, in 1691, John Lyon, 4th Earl of Strathmore and Kinghorne, by whom she had 10 children. Elizabeth Bowes-Lyon, Queen consort of George VI, was one of her many descendants.
SIR PETER LELY (1618 - 1680) was the most important portraitist in the reign of Charles ll, although he had painted portraits throughout the Commonwealth. Principal Painter to the King, he painted everyone of importance, maintaining a busy and active Studio to help with the huge demand for his portraits. Members of his Circle, many of them talented artists in their own right, emulated his style to supply this constant market.
SIZE: 18 x 15 inches canvas
23 x 20.25 inches inc. frame.
PROVENANCE: Cheshire Private Collection
Roy Precious - Antiques & Fine Art has dated this piece to the Before 1700 period.
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