Patek Philippe 5550P Perpetual Calendar Cal. 240 Q Si

Recently Patek announced the latest in the Advanced Research series, the ref. 5550P perpetual calendar fitted with the cal. 240 Q Si movement. This new calibre features a silicium escape wheel, anchor, hairspring and the latest innovation, a silicon balance wheel, labelled GyromaxSi after Patek’s adjustable mass balance. Together all the silicium escapement parts are termed surprise, surprise, Oscillomax.

The Advanced Research series began in 2005 with the ref. 5250P, followed by the ref. 5350P in 2006 and ref. 5450P in 2008. All were annual calendars based on the cal. 324, but with each of these watches Patek Philippe gradually introduced silicon components – Silinvar escape wheel, Spiromax hairspring and Pulsomax lever – into the escapement. Currently the Spiromax is standard on the CH28 movement of the 5980 and 5960 and in time to come the silicon hairspring will become standard on all Patek watches.

One of the advantages of the four silicon parts in the new cal. 240 Q Si according to Patek is a gain in efficiency, leading to a 70 hour power reserve instead of the regular 48 hours for the conventional cal. 240. The press release explains this in detail:

“It accounts for a significant increase of energy efficiency attributable to the innovative Oscillomax® subsystem, particularly of the Pulsomax® escapement and of the GyromaxSi® balance. This gain is based on the perceptibly lower mass of Silinvar® parts compared to conventional components, on the optimized geometry of the lever and escape wheel, and on the much-improved aerodynamics and mass distribution of the GyromaxSi® balance, to mention just some of the key reasons. Less energy dissipated means greater efficiency as demonstrated by a power reserve increase of about 50% without having necessitated any modifications of the mainspring, the frequency, or the moment of inertia of the balance. The efficiency of the winding train has also been perceptibly improved.”

GyromaxSi balance wheel in silicon with gold weights

Pulsomax escape wheel and anchor

Spiromax hairspring

Cased in platinum and identical in size to the ref. 5140 perpetual calendar at 37.2 mm, the ref. 5550P is features a silver dial with gold markers which I assume is similar to the dial on the ref. 5350P. Usually for a Patek perpetual calendar, but similar to the annual calendars, the ref. 5550P has luminous hands and markets on the dial. Like the other Advanced Research watches it is a limited edition of 300 pieces.

Click here for my thoughts on the Patek ref. 5270G, another of the new releases for 2011.

– SJX

I have the book by Leonardo Arte and it’s a beautifully illustrated publication with lots of large photos of vintage Pateks.



At SIHH earlier this year Panerai unveiled the Luminor Submersible 1950 3 Days Automatic Bronzo PAM 382, which quickly became one of the most talked about Panerai watches launched at the show. The PAM00382 Bronzo the first ever Panerai with a bronze case.

The PAM382 Bronzo at SIHH

Though bronze is a primitive alloy, it has certain useful qualities. Marine bronze like the type used in the Panerai Bronzo – nowadays used for things like ship propellers – offers superior resistance to corrosion and salt water, compared to steel.

But untreated bronze as used by Panerai PAM382 will acquire a patina, which is actually oxidation, over time. Once the surface layer of bronze has oxidised, it forms a protective layer over the rest of the metal.

The changes to the surface of the bronze alloy are front loaded, most of the patina occurs early in use because of the oxidation layer which gradually forms. That contrasts with conventional watch metals like steel or gold, which constantly suffer wear and tear with use.

The prototype Bronzo at SIHH

The prototype shown during SIHH was largely new and thus had only minimal patina; it still retained the copper tone of the bronze alloy.

Incidentally the Panerai bronze alloy is significantly more reddish than the bronze used Anonimo or Gerald Genta, which I assume means it has a higher proportion of copper.

Recently I had the opportunity to examine a PAM382 that had been handled over a longer period, resulting in significantly more oxidation. This watch is a prototype that has been shown to members of the press around the world. Though the patinated Submersible Bronzo looks somewhat like a grimy watch, it is actually attractive. The surface is variegated, with spots and patches of different shades. It sounds almost like the description of skin ailment but as the cliche goes, the case has character. And the resulting patina on the case matches the green dial perfectly.

Panerai collectors rank up there with vintage Rolex collectors as connoisseurs of patina, witness the reverence for vintage Panerai, or the attempts to artificially age leather straps by dunking them in olive oil for example, and so this watch will be a hit.

That, however, brings to mind an interesting issue. One of the key attractions of Panerai watches is the potential for appreciation and liquidity; Panerai watches are some of the most heavily traded.

But since the Bronzo acquires a patina over time, how will the watches be received on the secondary market? I can imagine bizarre attempts to keep it patina free. – SJX Update 17 March 2012: Photos of a month old Panerai Bronzo which has already developed a noticeable patina.

A closer look at the Bronzo with character

The Negretti Burton book (below right) is an excellent reference on Panerai; the other is a book on a yachting race that Panerai sponsors and authored by its CEO Angelo Bonati.