A fine and rare clockmaker's brass double-framed balance engine Attributed to John Wyke or Thomas Green, Liverpool, late 18th century The asymmetric 'D' ended double-frame enclosing 5 inch circular cast brass index plate fitted to turned brass centre-arbor with adjustment of bottom pivot via winged screw secured by a locking nut, the upper pivot passing through the frame to hold the work against an adjustable locking top pivot screw threaded into a curved brass support, the iron yoke-shaped cutter frame carrier mounted on a sliding bracket and fitted with pair of screw pivots, the side of the frame fitted with bracket for the index plate locking pin arm, together with detached geared crank handle, cutter carrier castings, loose screw pivots and a single cutter, (the index plate replaced and lacking holes), the frame 16cm (6.25ins approx) long. Balance wheel engines are essentially small wheel cutting engines designed to cut escapement crown wheels, although Swiss made examples survive in reasonable numbers English models are extremely rare. The current lot can be directly compared to examples appearing in contemporary printed trade catalogues by both John Wyke and Thomas Green illustrated respectively in Crom, Theodore R. HOROLOGICAL WHEEL CUTTING ENGINES page 103, figure 97 and Crom, Theodore R. Horological Shop tools 1700-1900 page 160, plate 61. It is clear that both of these illustrations are based on the same engraved plate suggesting that such engines were most likely made in a single workshop - probably that of John Wyke. Included with the current lot is a very detailed analysis of the various screw threads used compared with those found on a similar single-frame balance engine signed by Wyke (in the British Museum) and a wheel cutting engine signed by Daniel Sephton of Prescott. The conclusion of this analysis is that all three engines used use screw threads cut from the same tackle.