Reading Time: 7 minutes Key takeaways • Arnold & Son has released the Ultrathin Tourbillon Onyx Edition, featuring a 41.5 mm case available in 18-carat red gold or 950 platinum, with each version limited to only eight pieces. • The timepiece showcases a unique dial crafted from polished black onyx, complemented by a first-of-its-kind matte satin-finished onyx sub-dial and a flying tourbillon at 6 o’clock. • Driven by the in-house A&S8300 manual-winding calibre, the watch is remarkably thin at 2.97 mm and offers an impressive 100-hour power reserve. When John Arnold began his career in London in 1762, only a handful of leading watchmakers – including George Graham, Thomas Mudge and John Harrison – used pierced rubies to reduce friction at the pivots of the final wheels of the gear train and the balance. Long a closely guarded secret among English master watchmakers, John Arnold also employed this savoir-faire in jewels in the escapements of his marine chronometer...