This past March, at Baselworld 2012, Patek Philippe showed off their first ever regulator timepiece, the Ref. 5235 Annual Calendar Regulator. Consisting of a central minute hand, a subsidiary seconds dial (at 6 o’clock) and a subsidiary hour hand at 12 o’clock – the regulator dial separates the different time functions.

Regulator timepieces were used historically, to keep time as accurately as possible, specifically at workshops and observatories – where accurate timekeeping was paramount. Furthermore, to animate this all new functionality, Patek Philippe watchmakers created an all-new manufacture movement.

“When adjusting their timepieces, watchmakers needed an unobstructed view of the seconds hand, which is why the hour display was moved to an off-center location where it would not sweep over and thus partially cover the seconds dial for several hours in the course of a day.

One of the finest examples of this type of freestanding precision clocks is the Patek Philippe & Co. regulator built at the beginning of the last century. For many years it has been keeping the time unperturbed – second by second – in the office of Philippe Stern, the company’s honorary president.”

The Ref. 5325 features an  annual calendar function, which automatically recognizes 30-day and 31-day months and only needs to corrected once per year. To make the adjustment, corrector buttons are located on the upper left quadrant of the case flank: Date between 9 and 10 o’clock, Month at 10 o’clock, Day at 9 o’clock (comes with correction stylus in ebony and 18K white gold).

Powering Ref. 5325 is Caliber 31-260 REG QA, an ultra-thin self-winding movement with an Annual calendar with aperture displays for the month, day of the week, and date. The in-house caliber consists of 320 parts (basic caliber 181, Annual calendar 139), 29 jewels, a power reserve of 60-hours and an unusual frequency of 3.2 Hz (or 23,040 VPH). This is the first time in Patek’s history that a movement was designed from the very beginning to accommodate oscillator components crafted from Silinvar®, a high-tech material derived from silicon.

The Spiromax® balance spring and Pulsomax® escapement both utilize Patek’s proprietary Silinvar® material. “The enhanced isochronism delivered by the Spiromax® hairspring and the improved energy efficiency provided by the Pulsomax® escapement contribute significantly to higher rate accuracy and long-term dependability. Additionally, Silinvar® components are totally anti-magnetic, remarkably shock-resistant, non-corroding, and require no lubrication.”

Additional innovations include an extra-long mainspring, which allows for a 60-hour power reserve, with just one mainspring barrel. A new going train was designed in order to increase efficiency and to reduce wear. A 22K gold micro-rotor unidirectionally winds the mainspring.

Thanks to the ultra-thin movement, Ref. 5325 is presented in a very thin case. The 5325 has a fully polished 18K white gold case that measures 40.5 mm in diameter, and thanks to an ultra-thin movement, a height of only 11 mm. “The bezel is gently chamfered and the caseband is decorated with straight graining – a perfect match with the satin-finished dial.” The two-tone silvery gray dial features a vertical satin finish, and the two subsidiary dials have circular graining.

Hand-stitched night-blue alligator strap with 18K white gold prong buckle, engraved with Patek Philippe. Water-resistance 30 meters.

Retail is $53,600.

Posted by:Jason Pitsch

Jason Pitsch is the Founder of Professional Watches. He appreciates good craftsmanship in everything from architecture to automobiles to cameras to clothing. Yet his focus for the past decade has remained consistent on covering just one type: watchmaking.