The mirror frame is veneered with an unusual timber called cocus wood, a hard, dense wood with a chocolate brown heart and a yellow sapwood, often referred to, erroneously, as laburnum. It was imported from the West Indies and was often known as West Indian ebony. It was used as a cabinet wood between 1660-1740 and in the present instance, a section of cocus wood has been end-cut to provide a decorative "oyster"-veneer (A. Bowett, "Myths of English Furniture History: Laburnum Wood Furniture", Antique Collecting, June 1998, pp. 22-23).
The veneer on this looking glass is similar to that of a silver-mounted cabinet-on-stand at Windsor Castle, given by King Charles I's Queen, Henrietta Maria, to the Earl of St. Albans, c. 1665 (see The Dictionary of English Furniture, 1927, Vol. I, fig. 2, p. 163). A George I cocus wood card-table was sold from the Humphrey Whitbread Collection, Christie's, London, 5 April 2001, lot 365.