Wm Callaghan is listed as an optician in London directories between 1866 and 1892. Several of these chairs are known to exist and it seems to be accepted that they are for use with a telescope, although a similar chair illustrated in Architectural Review Decoration Supplement, July 1937 from the Catalogue of a Loan Exhibition Depicting British Country Life is described as a cherry sorter's chair. A related cair is illustrated in C. Gilbert, Furniture at Temple Newsam House and Lotherton Hall, Leeds, 1998, vol.III, cat. no. 684. Another was sold Christie's, London, 24 October, 2006, lot 26.