Pre-Patent Prototype Karrousel with Detent Chronometer Escapement S

Pre-Patent Prototype Karrousel with Detent Chronometer Escapement S. Smith & Son,Watchmakers to The Admiralty, 9, Strand, London, "English Revolving Escapement, Chronometer", No. 239. The case with London hallmarks for 1882-3. Extremely fine, exceptionally rare and possibly unique, large, heavy, keyless 18K yellow gold pocket chronometer with prepatent Bonniksen 52 1/2 minute Karrusel with spring detent escapement, the first watch of this series. Four-body, polished, heavy, "pomme et filet", by Frederick Thoms & Samuel Smith (master marks FT & SS). Hinged gold cuvette. hite enamel with radial Roman numerals, outer minute track, subsidiary seconds. Blued steel spade hands. 46 mm, frosted gilt, half-plate, going barrel, 52 1/2 minute karrusel carriage with foliate engraved cock, jeweled Earnshaw-type spring footeddetent escapement, free-sprung cut bimetallic compensation balance, blued steel balance spring with terminal curve, diamond endstone. Dial and movement signed. Diam. 57 mm. Notes This is almost certainly the first karrusel watch with a detent chronometer escapement; it is certainly the first watch of the famous “No. 239” series that established the record for number of marks obtained at Kew Observatory for pocket chronometers. The absence of the Bonniksen patent number indicates the watch was made before the 1893 patent of the karrusel; it is therefore of great historical interest in the development of precision watchmaking. This watch could be termed experim