Jaeger-LeCoultre

“Keyless pocket chronometer” Attributable to Marius Lecoultre, Rue Bonivard 8, Geneva, circa 1875. Very fine and possibly unique 18K gold hunting-cased, keyless, astronomical, retrograde perpetual calendar, pocket chronometer with phases of the moon and spring detent escapement and spherical hairspring. Five-body, "bassine et filets", solid, both covers engine-turned, front cover with black enamel monogram, glazed hinged cuvette. Notes The present watch is the only example of this type of ebauche we are aware of with keyless winding and perpetual calendar; furthermore it is one of only three watches with perpetual calendar, fusee, and detent escapement to have passed through these rooms in recent years. The ebauche used in this watch was reserved for high quality pocket chronometers mostly those made in Locle and Geneva in the third quarter of the 19th century. These ebauches are most often found on key-wound watches intended as high precision chronometers with detent escapements or tourbillon regulators and are rarely fitted with additional complications as these often detract from the timekeeping ability of the watch. The art of combining mechanical precision with complications is a challenge as the two are difficult to make coexist; generally speaking, complications interfere with the precision of the watch, due to the additional parts. To maintain a high level of precision and overcome the resistance of the additional springs, clicks, and wheels of a watch with pe