An unusual George II black japanned table clock with Dutertre`s duplex escapement. Indistinct ori

An unusual George II black japanned table clock with Dutertre`s duplex escapement. Indistinct original signature, circa 1740. The five pillar twin fusee bell striking movement with escapement composed of two escape wheels of varying diameter mounted on the same arbor which alternately engage with cranked pallets fitted with a standard verge type short bob pendulum, the backplate finely engraved with a grotesque mask within Ho-Ho bird inhabited foliate scrolls and a narrow ropetwist border, the 7 inch brass break-arch dial with calendar aperture to the matted centre within applied silvered Roman numeral chapter ring and Indian mask and scroll cast spandrels to angles, the arch with original signature boss bearing re-engraved script Tho Tompion, LONDINI (indistinct traces of original script visible on close examination) within a herringbone border and flanked by conforming mounts, the inverted bell-top case with foliate cast brass carrying handle above front door with scallop shell and scroll cast brass frets to upper quadrants, the sides with ruby glazed windows above blanked break-arch apertures, the rear with conforming glazed upper quadrants over break-arch aperture, the exterior decorated in raised polychrome and gilt with chinoiserie designs within foliate borders throughout, the cavetto moulded base with later brass bun feet, (finish rubbed, other relatively minor faults) 44cm (17.75ins) high excluding handle. The escapement in the current lot appears to be an early/contemporary application of the duplex arrangement as designed by the French horologist Jean Babtiste Dutertre (worked 1715-42), and was perhaps conceived as attempt to improve on the tic-tac escapement. The principle benefit is that the wear rate is greatly reduced as the pallets only engage once with each tooth for each rotation rather than twice (once from either side) for the standard tic-tac arrangement. In essence one wheel provides the entry action of a recoil arrangement and the second controls the exit. This division of the function of the escapement between two wheels allows the teeth on each wheel to be of a heavier profile than on the single escape wheel of a tic-tac escapement, further improving reliability and longevity. Dutertre`s design is illustrated in Reid, Thomas A TREATISE ON CLOCK AND WATCH MAKING plate IX/48 and is briefly described in Appendix B. The overall style, design and layout of the movement suggests London work from the second quarter of the eighteenth century. The engraving to the backplate is unusual being centred with a grotesque mask within a shaped reserve however the Ho-Ho bird foliate scroll infill is more typical of decoration found on London made clocks of the period. Overall the current lot has survived in original condition (including the escapement which is unaltered and has always been with the clock), however the erasing of the original signature to the boss in the arch is a shame as the name of maker of this unusual form of escapement has been lost, although further research and examination could result in a positive attribution.