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MB&F HM4 Kittyhawk – The Original HM4 Prototype Turned Into a Piece Unique

Nostalgia strikes hard at MB&F as the original prototype of the HM4 is transformed into a Unique Piece.

| By Rebecca Doulton | 3 min read |
MB&F HM4 Kittyhawk prototype piece unique noseart

MB&F takes a walk down memory lane as two of its icons celebrate their tenth anniversary. Two weeks ago we witnessed the release of the HM3 FrogX, a special 10-piece edition of the beloved HM3 Frog in transparent sapphire cases. Today, MB&F celebrates the tenth birthday of the Horological Machine No.4 with a unique piece made from the original titanium prototype and decorated with Kittyhawk nose art.

Curtiss P-40 Kittyhawk

Fans of WW2 aircraft will be familiar with the Curtiss P-40 Warhawk, a single-seat, single-engine American fighter plane that made its debut in 1938. Known as the Warhawk in the United States, the P-40 was adopted by most Allied powers during WW2, and the P-40D model was nicknamed Kittyhawk. The fighter plane was enlisted by Desert Air Force squadrons of the British Commonwealth in the Middle East and North African campaigns of June 1941. The famous No.112 Squadron of the Royal Air Force flew P-40s in North Africa and painted menacing shark’s teeth on the nose, eventually earning the title of ‘Shark Squadron’.

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the genesis of the HM4

Unlike many of MB&F’s watches that might have been concocted in outer-space, the design inspiration behind the HM4 is patently clear: the two prominent torpedo-shaped canisters look like the twin jet turbines of a fighter plane. Like so many MB&F creations, the idea behind the HM4 came from Max Büsser’s childhood passion for model aircraft. Introduced in 2010, the HM4 Thunderbolt won the Best Concept & Design Watch at the Grand Prix d’Horlogerie de Genève that same year.

MB&F HM4 First Edition
The original MB&F HM4 Thunderbolt edition, from 2010.

The surprising configuration of the HM4, with its twin pods for the hours/minutes (right turbine) and power reserve (left turbine) and exposed balance wheel in the central horizontal section, required the development of an unprecedented movement. HM4’s engine was designed and developed by MB&F with the help of Laurent Besse and Beranger Reynard. Capable of remaining airborne for 72 hours non-stop, the fuel is stored in two mainspring barrels and transferred to the turbines via vertical gear trains. Viewed from above through the transparent sapphire section of the case, a streamlined cock supports the balance wheel, which in turn reveals the oscillating wheel. Viewed from the undercarriage, sapphire window panes display the meticulously finished parts and the brand’s iconic battle-axe posing as a bridge. Two crowns, one for setting the time and the other for winding the movement, are integrated into the twin turbines at the rear of the case.

MB&F HM4 Kittyhawk prototype piece unique noseart
The new MB&F HM4 Kittyhawk

Appearing in various guises over the years, the first edition was the HM4 Thunderbolt of 2010 followed by Razzle Dazzle and Double Trouble in 2011. In 2012 a limited edition in red gold, titanium and sapphire, the HM4 RT, was produced until production was finalised with the HM4 Final Edition of 2013. There have also been some unique pieces produced for the Only Watch auction like this HM4 complete with a panda at the controls.

From a prototype to the HM4 Kittyhawk

The very complexity of the HM4 limited its production to just 100 pieces over the past ten years. However, there was one vestige of the HM4 in the form of a prototype. To honour the tenth anniversary of the HM4, MB&F has dusted off the titanium prototype and painted it with the iconic shark teeth and eyes of the P-40 Kittyhawks. To apply the nose art, microns of titanium were removed from the sides of the fuselage before miniature-painter Isabelle Villa painted the sharp teeth and angry eyes. To protect the miniature painting, a final coat of transparent varnish was applied.

MB&F HM4 Kittyhawk prototype piece unique noseart

Like all other editions of the HM4, the three-part titanium case construction is beautifully finished with polished and brushed surfaces, and the sapphire panes are intricately machined and polished to provide crystal clear views.

MB&F HM4 Kittyhawk prototype piece unique noseart


The HM4 Kittyhawk is a unique piece, and the price is upon request. For more information, visit MB&F.

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