A Cartier clock whose diamond-set hands form a dragon and appear to float in mid-air will headline Phillips' Geneva Watch Auction: XXIV on 7 and 8 November 2026. Portico Mystery Clock No. 4, made in 1924, is offered as lot 220 with an estimate of CHF 1.8 million to CHF 3.6 million, or roughly $2.19 million to $3.9 million, at the Hotel President in Geneva.

Only six Portico Mystery Clocks left the Cartier workshops between 1923 and 1925, and No. 4 is the sole example with a hexagonal dial. The mystery-clock mechanism hides its workings so the hands seem suspended in the frame, a trick that made the series a showcase of Cartier's interwar craftsmanship. The piece has not appeared at auction since 19 November 1996, when it featured in a Geneva sale devoted to the magical art of Cartier.

Its closest relative offers a guide to what it might achieve. Portico No. 3, also made in 1924, sold at Phillips in Geneva in May 2025 for CHF 3,932,000. That result sits above the top estimate now placed on No. 4, suggesting the house has priced the rarer hexagonal example with room for competitive bidding.

The clock will be on public view from 4 to 7 November ahead of the sale. Phillips is presenting the Geneva auction in association with Bacs & Russo, and estimates are quoted before buyer's premium. The six Portico clocks were made over just three years, and the hexagonal-dial example has spent three decades out of public view since its last sale, making its reappearance one of the most closely watched lots of the Geneva November season.