The Arnold & Son Constant Force Tourbillon 11 Platinum Edition, reference 1FCBX.Z01A.C0232X, is a hand-wound tourbillon with a constant-force mechanism. The polished platinum case measures 41.5 mm in diameter and 13.7 mm thick, with a domed sapphire crystal, a sapphire caseback and 30 m water resistance. The dial base is solid 18k yellow gold, hand-engraved with an irregular fern pattern, and carries an off-centre concave white opal subdial with black Roman numerals and flame-blued hands. The one-minute tourbillon sits in an aperture in the lower right of the dial, topped by an 18k gold constant-force bridge and a flame-blued deadbeat seconds hand shaped like an anchor. The calibre A&S5219 is manually wound, measures 33 mm across and 10.48 mm thick, runs at 21,600 vph (3 Hz) and stores 100 hours of power in twin barrels.

The Constant Force Tourbillon 11 pays tribute to Abraham-Louis Breguet’s tourbillon and to John Arnold, whose fusée-and-chain system is replaced here by a constant-force device that evens out the energy delivered to the escapement. The two watchmakers were friends, and a plate on the caseback is engraved with a dedication to their memory. The model first appeared in 2025 in yellow gold with a white Grand Feu enamel dial at CHF 129,800. The platinum edition followed in November 2025 at Dubai Watch Week, with the engraved dial inspired by the fern-covered moors around Tintagel in Cornwall, Arnold’s birthplace. It comes on a midnight blue alligator strap with a platinum folding clasp. The price is CHF 140,600, and the edition is limited to 11 pieces.

Monochrome reviewed the yellow gold original favourably, praising the depth of the enamel dial, the anchor-shaped seconds hand as a nod to marine chronometers and the finishing of the movement, while describing the 30 m water resistance as modest. Readers under that review were divided: some placed it alongside work from leading independents, while others criticised the proportions between dial and case and found the watch slightly too thick. For the platinum edition, Monochrome singled out the engraved gold dial and the way its irregular pattern catches light, and judged the 41.5 mm case sizeable but justified by the space the tourbillon and constant-force mechanism require. The Constant Force Tourbillon 11 Platinum Edition is a limited edition of 11 pieces, available through Arnold & Son retailers as of October 2026.