Watch Auctions

The Clock That Belonged to Cartier’s Grandson: Portico No. 4 Is the Most Overlooked Lot at Geneva 2026

If you’ve been tracking the Geneva auction week build-up, you’ve read about the Pucci Papaleo Rolex collection, the Sultan Qaboos Nautilus, and the extraordinary Francis Picasso movement pieces. But five days from the first gavel, one lot at Phillips Geneva Watch Auction XXIV is still nearly invisible in the conversation: Lot 220, a 1924 Cartier Portico Mystery Clock that weighs 10.6 kilograms, once belonged to Louis Cartier’s own grandson, and has not traded publicly in 30 years. It deserves far more attention than it’s received.

What Is a Cartier Portico Mystery Clock?

The Portico series sits at the summit of Cartier’s entire output in clocks. Between 1923 and 1925, Louis Cartier and Swiss-born watchmaker Maurice Couët produced exactly six Portico Mystery Clocks — monumental Art Deco objects that fuse a temple-like architectural form with Cartier’s signature “mystery” movement, in which the hands appear to float with no visible connection to any mechanism. The trick is a pair of crystal discs, each with a thin concealed gear ring, that rotates the hands while the movement remains hidden in the upper arch. A century on, the effect still feels like sorcery.

All six Porticos were displayed together in public only once, at a 1991 retrospective. Since then they have dispersed to private collections and to auction — becoming, in the process, one of the most sought-after categories in decorative objects at the world’s leading watch sales. They occupy a space that sits between Cartier’s watchmaking heritage and the highest tier of 20th-century applied art. When one appears, the market pays attention. Or should.

Portico No. 4: What Makes It Singular

No. 4 is distinctive even within the Portico family. It is the only one of the six to have a hexagonal rock-crystal dial. All five others carry 12-sided dials; No. 4’s hexagonal form gives it a subtly different rhythm — slightly more controlled and classical in its geometry, though no less monumental in presence. The four square columns of rock crystal that frame dial and movement rise to 38.5 centimetres in total height. The structure weighs 10.6 kilograms — a reminder that “clock” barely captures what this object is. It is a sculpture that tells the time.

The material specification is exceptional. Jadeite jade, onyx, seed pearls, mother-of-pearl, and diamonds are combined in the base and columns. The hands — the final, irreducible magic trick of a mystery clock — are fashioned as diamond dragons in pavé-set rose-cut stones, one of the most evocative details on any of the six pieces. The movement itself was made by the European Watch and Clock Company, wound by hand, and sits in the upper arch where it remains essentially invisible from the front. A Cartier certificate dated 2002 accompanies the lot, confirming that the house itself authenticated and catalogued the piece at the start of this century.

Phillips’ Aurel Bacs has written that “Portico No. 4 stands in a league of its own.” Given that Bacs has seen more top-tier decorative Cartier at auction than virtually anyone alive, and given that the hexagonal dial does genuinely make No. 4 unique within an already uniquely rare series, that verdict carries weight.

Provenance: From a Maharajah’s Palace to Alain Cartier’s Collection

The ownership history of Portico No. 4 is the kind that serious collectors build careers around. Research by Phillips suggests the clock’s earliest documented owner was the Maharajah of Nawanagar — one of the most extravagant of the Indian princely rulers in the interwar years, and precisely the sort of client for whom Cartier produced its most ambitious objects. The idea of a Portico Mystery Clock commissioned for or acquired by an Indian royal in the 1920s is entirely consistent with what we know of both Cartier’s production and Nawanagar’s tastes.

From there, the trail leads to Alain Cartier — grandson of Louis Cartier, and the last president of Cartier S.A. before the company passed out of family ownership in 1979. That Alain Cartier should have acquired one of the six Porticos is not surprising: it is exactly the kind of object that would draw someone who grew up surrounded by the firm’s finest work and understood its historical significance more intimately than any outside collector could. After Alain Cartier, the clock passed to private hands. Its last public appearance was a Geneva sale in November 1996. It has been silent for thirty years since then.

What the Numbers Say About the Estimate

The estimate of CHF 1,800,000–3,600,000 sounds substantial — and it is. But the closest market comparator suggests it may also be conservative. In May 2025, Phillips sold Portico Mystery Clock No. 3 — the other large, complex model in the series — for CHF 3,932,000, against a pre-sale estimate of “In excess of CHF 2,000,000.” That result was nearly double the floor, and the hammer fell at one of the highest levels ever recorded for a Cartier decorative object at auction.

No. 4 comes to market with a higher ceiling estimate (CHF 3.6 million versus No. 3’s open-ended floor) but with an equally strong case. The hexagonal dial arguably makes it rarer within the series — there is, by definition, only one Portico with that form. Whether that rarity translates into a premium over No. 3’s result depends on the room on the day. Buyers tracking Cartier’s long-term value data will note that top-tier Cartier decorative objects have consistently outperformed estimates at Phillips across multiple recent cycles. The high estimate is a reference point; history suggests the destination may be somewhere beyond it.

Attending and Bidding

The Portico No. 4 falls on Day 1 of the Phillips sale — Saturday 7 November — alongside the full roster of exceptional lots covered in our Phillips XXIV preview, including the Pucci Papaleo Rolex collection. Previews at the Hotel President run Tuesday 4 to Friday 7 November. For a full breakdown of all four houses across the week — sessions, timings, logistics — see the Geneva auction week session guide. Absentee bids, phone lines, and online bidding are all available directly through Phillips at phillips.com/auction/CH080426.

Sources: Phillips editorial, “The Story of The Cartier Portico Mystery Clocks” (27 October 2026); Titanium.lv, 29 October 2026.