On Friday, the watchmaker revealed a very personal and very rare Patek Philippe Minute Repeater Alarm Philippe Stern, Ref. 1938P-001. The watch is a tribute from Patek Philippe president, Thierry Stern, to his father, former Patek Philippe president, Philippe Stern on the occasion of his 85th birthday. The watch, rather unusually, features the face of Stern Sr., rendered in a white and gray miniature portrait executed in grand feu enamel on a grand feu enamel black dial (“Email” beneath the seconds counter means “enamel” in French). It’s a touching gesture from son to father, however, one wonders which collectors will want to wear the elder Stern’s on their wrist. But Patek Philippe Minute Repeater Alarm Philippe Stern aficionados might appreciate what’s beneath the surface. Not surprisingly, Thierry Stern went all out for this appreciation piece, which houses a brand new Caliber R AL 27 PS. The movement combines the Swiss brand’s famous R 27 caliber, used in its Grandmaster Chime Ref. 5175 for the company’s 175th anniversary, with a 12-hour alarm function chiming a programmed time, read via the 18-karat rose-gold Breguet-style hand. And what’s more, the new caliber will be used only in the 30 iterations of this watch and never employed again, increasing the rarity of the timepiece. The movement is visible beneath a hunter caseback engraved with “A Mon Père, 85 ans de passion horlogère” (“To my Father, 85 years of watchmaking passion”) on the cover. Beneath the sapphire crystal glass, another sentimental touch was added to the 22-karat yellow-gold rotor, which is adorned with an engraving of Philippe Stern’s signature. Driving home even further the special nature of the piece are the chamfered edges of the bridges and hammers, which are gilded.

The self-winding caliber R AL 27 PS takes the alarm function and integrates it into the caliber R 27. Patek Philippe Minute Repeater Alarm Philippe Stern engineers had to rethink the minute repeater mechanism to combine the two. Both the alarm and the minute repeater chime on the same two gongs. Once activated via the slide piece on the left flank of the case, the movement can either instantly strike the time on the dial in minute repeater mode or put the stake on hold until the time displayed corresponds to the scheduled alarm time. The two modes are indicated via the bell-shaped aperture beneath the Patek Philippe signature. When in minute repeater mode, the bell is black; in alarm mode the bell is red. A push-piece in the crown allows the user to choose between the two. When in alarm mode, the slide must be actuated again to wind the alarm, changing the bell from red to white. When in alarm mode is white, it means that the alarm has been set but has not yet sounded. While the bell is set to white it’s possible to return to minute repeater mode by pressing the push-piece without the striking mechanism being activated. Like a traditional minute repeater, the piece will sound the hours, quarters, and minutes on demand, but the 12-hour alarm, which is set from one quarter-hour to the next via the crown pulled out in its middle position, strikes two minutes before its set time in order to allow the maximum number of chimes (thereby providing more of a melody). For instance, if the alarm is set at 3 o’clock it would actually go off at 2:58, so the user would hear two low-pitch strikes for the hour, three double high-low strikes for the quarters, and 13 high-pitch strikes for the remaining minutes.

All in all 227 parts had to be added to the movement to accomplish its technical feats. Plus, four new patents were filed for a unidirectional coupling mobile system, a timepiece incorporating a minute repeater and alarm with reversible selection, a timepiece with a repeater and constant-travel slide piece, and a striking mechanism equipped with a delaying device.

The piece is limited to just 30 pieces worldwide. While Patek Philippe Minute Repeater Alarm Philippe Stern collectors may not be sold on wearing Philippe Stern’s face, Patek Philippe enthusiasts may want to get their hands on a piece for the art of its mechanics and, of course, to have the bragging rights of owning the most elevated complication from one of the most coveted (and hard to get) watch brands on the planet.