Classic Meets Cutting Edge In The De Bethune DB25 Perpetual Calendar

The perpetual calendar has of course been on our minds (and everyone else’s who is interested in complicated watchmaking) quite a bit and though we are edging away from Leap Day and towards the Ides of March, the almost infinite design and technical possibilities that the perpetual calendar offers means that there’s no shortage of interesting variations on the theme to explore. De Bethune produced its first perpetual calendar, the DB15, in 2004, and over the years it has existed in several different variations in case materials, colorways, case sizes, and movements. The DB15 of 2004 was launched just two years after the brand itself, which debuted in 2002, and it was followed in 2005 by the DB17, which offered some design tweaks to the DB15 design as well as some changes to the movement. In 2010, the DB25 was launched at the GPHG, in a 44mm case, and it in turn was followed by a smaller, 40mm model in 2022.

Right at the outset the first point to note about the DB25 Perpetual Calendar (DB25QPARS1) is that it was De Bethune’s very first automatic perpetual calendar. The DB15 and DB17 both used De Bethune’s hand-wound caliber DB2004, with its characteristic delta-shaped bridge. DB25 however added another layer of complexity to De Bethune’s perpetual calendars, with the self-winding caliber DB2324 QP. One of the advantages of a self-winding perpetual calendar is of course the fact that you can keep the watch on a winder and the calendar indications will stay up to date (the first self-winding perpetual calendar came along fairly late in the day, relatively speaking, when Patek Philippe launched the 3448, in 1962).

The DB25 QP at 44mm is a fairly large watch and as Tim Mosso mentions in his video review, you do sort of have to be on Team Big Watch if you are going to wear it.

The lugs however sit low on the case and the strap hugs the wrist very comfortably (this is not an ultra-thin perpetual by any means however it is not inordinately thick, at 11.1mm). The somewhat architectural and slightly imposing presence of the watch is in any case deliberate, and part of the appeal of the DB25 perpetual if you find it appealing at all. The lugs do a lot to open up the design – they are openworked, and tipped with small ogival shapes which are an echo of the more overt ogival lugs found on other De Bethune watches. Over the last couple of decades De Bethune watches have consistently used these ogival lugs in their watches, though how they are implemented has varied, ranging from the fairly subtle version in the DB25QP to the more assertive shapes found elsewhere in De Bethune’s history (occasionally but rarely they are omitted, as in the DB20).

The basic elements of the design do not diverge significantly from those of a real classic perpetual calendar – the day and month are shown in windows at 3:00 and 9:00, and there is, in accordance with the standard practice for perpetual calendars going all the way back to the pocket watch era, a sub-dial for the date and a moonphase display.

The way in which these elements are implemented, however, and how they interact with other elements of the dial design, set the DB25QP apart from all other perpetual calendars. Moving from the outside in from the slim bezel, there is a ring of guilloché, a chemin-de-fer (railroad) style minute track, and then very dignified Roman numerals for the hours. The central part of the dial is decorated with a radiating guilloché pattern, and the lines between each sector of guilloché correspond to the hours.

The dial side of the watch also makes extensive use of heat bluing, in which various metals (at De Bethune, steel and titanium) are heated by hand over the open flame of an alcohol lamp until a layer of blue oxide forms, which is about as old-school a technique as you will find in watchmaking. The hands of the DB25 perpetual are heat-blued steel, as is the background disk for the moonphase display (which is decorated with yellow gold stars set into four-lobed apertures – much more three dimensional than the usual practice of stamping the stars on the moonphase disk). Finally, there’s the spherical moonphase – one hemisphere is palladium, and the other is steel. The two hemispheres are bonded together and then heated – the steel turns blue at the normal temperature while the color of the palladium remains unchanged.

The movement is likewise a representative of both horological tradition and modernity. The modernity on display is not however not merely a question of appearance alone, or simply stylistic – this is not a movement which establishes its contemporary credibility by finishing the plates and bridges in black DLC.

Instead, it is a movement in which many of the basic elements of an automatic watch have been re-imagined and re-engineered.

To me one of the most exciting elements in this or any De Bethune watch, is the balance. Over the last 20 years, De Bethune has experimented with more variations on a standard balance than any other company, which is remarkable. Generally speaking, balances come in two flavors and just two flavors – standard annular balances, with balance springs whose active length is controlled by a regulator, and freesprung, adjustable mass balances, without regulator, which have a rate controlled by the timing weights on the rim. The latter is usually what you go with, if you want precision timekeeping with a reliable rate, and classic examples include Patek’s Gyromax balance, the Rolex Microstella screw system, and the various freesprung balance and silicon balance spring combinations used by Swatch Group in everything from the Tissot Powermatic 80 calibers, to the movements with co-axial escapements.

De Bethune, on the other hand, has in the caliber DB2324 QP, used a non-annular balance.

Instead of a continuous ring, the balance of the caliber DB2324 QP has four distinct arms, made of heat-blued titanium. At the end of each arm is a platinum timing weight, in the shape of an elongated, pointed oval. These weights are held in place by mounting screws and they can be adjusted inwards or outwards in order to change the rate of the balance. In principle, this is the same as the adjustable timing weight system used in balances like the Patek Gyromax or the Rolex Microstella, but there are obvious differences as well. The basic idea here is to ensure that as much of the mass of the balance is distributed on its circumference – conventional balances are designed with this in mind as well but the DB balance takes the principle much further. Not coincidentally it’s also beautiful to look at as well. The balance spring is also unusual – it is assembled in two parts, with the outermost coil intended to ensure that the coils of the spring remain as concentric as possible as the balance spring winds and unwinds. This is the same advantage offered by an overcoil balance spring, but without the additional height that a Breguet or Phillips overcoil requires.

And from a design standpoint, it is of course no coincidence that the ogival shape of the platinum weights echoes the ogival-shaped lug tips.

The balance assembly is fixed in place by De Bethune’s unique “triple pare-chute” antishock system, which in addition to offering better shock resistance than just a standard set of antishock springs, also re-centers the balance more rapidly if the watch does receive a shock.

Unusually, the rotor has its own antishock system, in the form of four flat blade springs each of which has three arms, which press against the two blued titanium arms of the rotor. The actual winding mass is a semicircle of white gold.

The DB25 perpetual is a rare watch – there are as far as I know, less than a dozen and in terms of innovative watchmaking, I don’t think it has any real peer or near-peer competitors when it comes to the foundational elements of the movement (the automatic winding system, balance, and balance spring).  It’s unquestionably an exotic and overtly technically advanced timepiece. But the elements of advanced engineering in the watch also contribute to a unique aesthetic. Advances in technical watchmaking tend to be either so discreet that they might easily pass unnoticed, or they’re so aggressively and obviously executed as to take the watch completely away from any connection to traditional watchmaking. The DB25 perpetual on the other hand, succeeds in combining both advances in engineering, and traditional watchmaking crafts, in a way that synthesizes both without losing the distinct identity of either.

See it here