This is a JLC ref 141.010.1, which is from 1983 and was a special release for the 150th anniversary of the company's founding. Movement is a manual-wind triple calendar moonphase, reportedly NOS from the 1940s. Movement is running well but unknown service history. Made of 18k yellow gold, dimensions: width 24 mm, length: 41 mm, thickness 9.5 mm, rectangular shape. It is in very good condition and does not seem to have been polished. Comes with blue ostrich leg strap (from the Strap Tailor) with the original gold JLC pin buckle. No box, no papers. It is #258 of 600. Price: $6250 USD shipped within the USA. Comparable listings on Chrono24 are upwards of $8500 Bank wire preferred. Plenty of references here on the reddits.