Y A Victorian rosewood small five-glass library mantel timepiece John McLennan, London, mid 19th century The four pillar single fusee movement with anchor escapement regulated by disc bob pendulum with holdfast to the shouldered backplate, the 3.5 inch square silvered brass Roman numeral dial signed John McLennan, London and numbered No. 9011 to centre, with blued steel moon hands and fine leafy scroll engraved spandrel decoration, the case with generous bevelled top glass to the tablet upstand over cavetto cornice and fluted frieze, the front with silvered canted insert to the interior of the glazed dial aperture, the sides with bevelled glasses and the rear with rectangular glazed door, the base with generous ogee outline waist over moulded skirt with squat bun feet, 23cm (9ins) high. John Osbourne McLennan was born in Dingwall, north of Inverness, Scotland in 1814. He was a highly accomplished watch and chronometer maker who worked for James McCabe junior and Charles Frodsham. He is reputed to have invented the duo-in-uno balance spring which was challenged by A.P. Walsh, however, as Tony Mercer notes in Chronometer Markers of the World: 'W. B. Crisp suggests that A.P. Walsh saw them at an exhibition of 1862 went home and copied them, then immediately had them displayed in his own showcase.' To demonstrate his design of duo-in-uno spring McLennan incorporated it into perhaps the smallest pocket chronometer ever made. Indeed the the example displayed at the 1862 Exhibition survives (No. 2164) and was sold at Christies, Geneva Important Watches 16th May 2011 (lot 110) for £30,000 CHF; and then at Sotheby's THE CELEBRATION OF THE ENGLISH WATCH PART IV 6th July 2017 (lot 65) for £60,000. John McLennan died in 1886 and was described in his obituary (published in the January 1887 issue of the Horological Journal) as probably the best all-round watchmaker of his time.