1912 One Hertz | Steel

This steel, Grönefeld 1912 One Hertz is one of the earliest wristwatches made by the brothers, after their Tourbillon Minute Repeater. Designed by the Grönefeld brothers in the Netherlands, the One Hertz movement was developed with the assistance of famed complications specialist Renaud and Papi in Switzerland, where Bart and Tim Grönefeld spent a number of years at the heart of the manufacture. Though subsequent pieces have since been made in a range of case materials, the One Hertz was initially launched in 2010, with a limited production of just 12 pieces in steel.

The Grönefeld brothers

The Grönefeld brothers’ upbringing in a small town in the Eastern part of the Netherlands was permeated in horology. In the evenings and on the weekends, as children, they used to play in their grandfather Johan's workshop, surrounded by instruments and by the sound of their ceaseless ticking. As a gifted watchmaker, Johan also looked after the clock of the nearby church, dating back to 1240. On his death, this custodianship was passed onto his son, the Grönefeld brothers’ father. The year the Grönefeld name was established in watchmaking was commemorated in the reference of the '1912 One Hertz'.

Watchmaking having made a strong imprint on them in their respective youths, Bart and Tim Grönefeld both trained in horology, cutting their teeth at famed complications specialist Renaud et Papi, alongside notable contemporaries such as Stephen Forsey and Stepan Sarpaneva. Producing no more than 70 watches a year, the Grönefeld brothers create extremely high-quality pieces, having commanded the admiration and respect of none other than Philippe Dufour, amongst others.

The One Hertz Movement 

One of the more obscure complications in horology, the 1912 One Hertz incorporates a deadbeat seconds, rarely found in contemporary watchmaking. An interesting complication for the brothers to tackle early on, the original deadbeat escapement goes all the way back to 1675, when it was invented by Richard Towneley for use in regulator clocks at the Greenwich Observatory. The complication itself is demonstrated through the jumping seconds snapping into position, contrary to the majority of mechanical watches where the second hand glides smoothly between passing seconds. Specialists in complicated watches, the Grönefeld’s intent to follow their Tourbillon Minute Repeater with a simple, time-only watch was always going to evolve into something mechanically more intriguing.

In the case of the One Hertz, Bart and Tim designed their movement to operate using two gear trains, based on two synchronised spring barrels feeding two separate (but linked) movements – one for the hours and minutes and the other for the seconds. According to Bart Grönefeld, the parts for the One Hertz movements were machined by Renaud et Papi in Switzerland, before being shipped to the Netherlands to be finished, painstakingly decorated and assembled in the Grönefeld workshop. The movement features over a dozen different finishing techniques, from snailing to frosting. The bridges, shaped like the bell gable roofs of Dutch houses, are fashioned out of steel, which is much more difficult and costly to work with, than brass or silver.

Each individual bridge requires dozens of steps and up to ten hours of work, including mirror polishing of the screws, and chamfering rims and slots, demonstrating the brothers’ fascination with depth and light. The overall dimensionality is reminiscent of A. Lange & Söhne, or even fellow Renaud et Papi alumni Greubel Forsey.

A coherent design

In traditional fashion, the Grönefelds imagined their desired dial layout first, before figuring out how to make a suitable movement to match. The deadbeats seconds occupies a central place, emphasised through the large seconds sub-dial - a sapphire disc raised above the other indications and metallisised. By comparison, the subsidiary dial for the hours and minutes are discretely located above, extending within the seconds indication. The overlapping portion of the sapphire disc is transparent, so as to not obscure the hours and minutes.

Encased within the large seconds sub-dial is the recessed power reserve indicator, highlighted by a frosted surface. The crown position indicator for “winding” and “setting” is similarly textured. Toggling between the two modes involves using the push-button crown, hacking the movement during setting - a system reminiscent of the clutch mechanism found in a number of Richard Mille models, also machined early on by Renaud et Papi.

The case, measuring 43mm across and 13mm thick, is made out stainless steel. It features brushed case sides, with polished caseback and bezel portions, giving the One Hertz a classically finished appearance. Despite its imposing size, it wears comfortably on the wrist, owing to the choice of case material and downturned, sculpted lugs.

The Set

This steel, Grönefeld 1912 One Hertz is accompanied by its original box and paperwork. It comes on a bespoke Helsinki grey nubuck leather strap, with curved ends, and also includes the original alligator strap and Grönefeld steel buckle.

Closer look

Condition

This Grönefeld 1912 One Hertz watch comes as a full set, with its original box and papers. The watch is in excellent condition and has perfect mechanical functionality.

Warranty

The watch comes with a two-year warranty from A Collected Man, alongside a lifetime guarantee of authenticity.