A FINE FRENCH LOUIS XVI SILVER CASED CONCENTRIC CALENDAR POCKET WATCH WITH SULLY'S ESCAPEMENTMICHAU, PARIS, LATE 18TH CENTURYThe gilt full plate fee movement with four columnar pillars and Sully-type frictional rest escapement regulated by sprung three-arm monometallic balance, the backplate with fine foliate scroll pierced and chased balance bridge, R/A regulation lever and signed Michau, A PARIS. No. 3842 to outer edge, the convex white enamel dial with very fine scripted signature Michau a Paris within concentric day of the week markers annotated in red abbreviated French and alternating with the zodiacal symbol for the opposing day as indicated by the elongated tail of the inner hand, the chapter ring with vertical Arabic hour numerals, dot minute track and blued steel hands, the outer track with date of the month in red Arabic numerals indicated by a brass arrow pointer, the rear of the silver consular case with engraved woodland scene of a hunting dog disturbing wildfowl within engine-turned border set behind a convex glass within gilt repeating foliate motif decorated bezel, the front with conforming bezel and the circumference with moulded bands beneath spension post with hinged loop.The backplate 42mm (1.625ins) diameter; the case 56mm (2.25ins) diameter. An Etienne Michau is recorded in Baillie, G.H. Watchmakers & Clockmakers of the World as working in Paris 1782-9. The current lot employs Sully's design of frictional rest escapement as ed by Pierre Le Roy in his 'Petit Ronde' marine timekeepers. The operation of this escapement and why it was chosen by Leroy is discsed by Claude Sabrier in an online article (posted on antique-horology.org) entitled Pierre Le Roy's 'PETIT RONDE'. Sabrier notes that Le Roy's principal motivations for ing Sully's escapement was the minimal friction of its operation (due to the pallets being very close to the balance arbor) and the possibility of making the escape wheel very light by cutting the teeth as long spokes. However fitting an escapement of this design to a watch presented some challenges principally in amodating a vertically orientated escape wheel of meaningful diameter requiring a slot to be cut through the frontplate to allow additional clearance. In addition to ing Sully's watch escapement the current lot is notable for having a very fine enamel dial, in particular the beautifully scripted signature which has lower case characters measuring less than half a millimetre high.