In 2011 , online watch collector’s forum, The PuristS will be celebrating their tenth anniversary and Swiss watch maker MB&F presents HM3 Chocolate Frog timepiece collection to honour the occasion. The “Chocolate Frog”, a limited edition of only 10 pieces, is a world first for MB&F, demonstrating the deep relationship between the brand and The PuristS, as it is the first model created specifically for a third party.
The protruding eyes of the (amphibian) frog enable it to see in many directions without having to turn its head. The bulbous domes of the HM3 Chocolate Frog have the opposite, but no less important, feature of enabling the time to be easily seen from many angles without having to turn the wrist. The Frog differs substantially from HM3 in that it is the aluminium domes that rotate under the sapphire crystals in the Frog, whereas it is the hour and minute hands that rotate around their respective stationary cones on HM3.
Rotating domes of this size and shape posed MB&F with a number of technical challenges. The hour and minute domes are machined from solid aluminium – chosen for its optimal strength to weight ratio. The domes weigh in at just over 0.5g. They are milled first from the outside and then the inside to arrive at a paper-thin wall thickness of just 0.28 mm, which reduces their energy requirements to an absolute minimum. Even the fabrication of the semi-spherical sapphire crystal domes was incredibly demanding and only recently even possible at all. This is due to the fact that any slight imperfection in the sapphire might introduce a disconcerting magnification effect. The sapphire has to be shaped and polished to be perfectly uniform.
The Frog’s unusual method of indicating time necessitated the development of a new gear train for the HM3 engine. This was because the aluminium hour dome of the Frog rotates in 12 hours compared to the 24-hour revolution of the HM3 hour hand. And as the oversized date wheel is driven from the hours, the gearing driving the date had to be reworked as well.
The Chocolate Frog may portray the time in a playful manner, but there is nothing but serious and meticulous attention to detail and care regarding the fine hand-finishing of the high-tuned engine purring within its lightweight high-tech titanium case. A close inspection of the case is rewarded with carefully thought out detailing including a figure 8 engraved around the domes that mirrors the form of the display back (revealing dual ceramic bearings); distinctive clover-head white gold screws; and an engraved arrow discreetly indicating the easy to read over-sized date. If the viewer’s gaze manages to break away from the bulbous indications, it is likely to be arrested by the brightly coloured 22K gold battle-axe winding rotor and the intricacies of the thoroughbred movement beneath.
The HM3 Chocolate Frog is a limited edition of 10 pieces featuring a chocolate PVD coated Grade 5 titanium case and a 22k red gold “battle axe” automatic winding rotor. It is available exclusively from www.PuristSPro.com.
Three-dimensional horological engine designed by Jean-Marc Wiederrecht/Agenhor; Girard-Perregaux base
Balance oscillating at 28,800 bph.
22K red gold battle-axe shaped ‘mystery’ automatic winding rotor
Hour and minutes information transmitted via ceramic ball bearings to rotating domes.
Number of jewels: 36 (all functional)
Number of components: 304
Hour on one dome (aluminium dome rotating in 12 hours)
Minutes on second dome (aluminium dome rotating in 60 minutes)
Date around the movement
Chocolate PVD coated grade 5 titanium/22K red gold rotor; limited edition of 10 pieces
Dimensions (exclusive of crown and lugs): 47mm x 50mm x 16mm
Number of case components: 53
Sapphire crystals: Domes and both display backs with anti-reflective treatment on both faces
Rotating aluminium domes – 0.58g
Black hand-stitched alligator with 18K red gold & titanium custom designed deployment buckle