MB&F Horological Machine No4 Final Edition

Horological Machine N°4 Final Edition

HM4 Final Edition – Easy to see, virtually impossible to catch!

Stealth. If you look at any plane or boat designed with stealth in mind, they usually look to all intents and purposes anything but inconspicuous. And the stealthier they are, the more strikingly – radar excepted – obvious they are.

Lockheed’s sensational F-117 Nighthawk was the world’s first operational stealth aircraft. While visually unmistakable, the F-117’s flat, faceted panels reflected radar away from detection and its dark surfaces blended seamlessly with the night sky. The Nighthawk was also revolutionary in the fact that its structure was a mix of aluminium and titanium.

Like the iconic F-117, HM4 Final Edition features square angular panels, dark surfaces and high-tech titanium. It looks fast. It looks menacing. And to date there have been no reports of a Final Edition being picked up by radar, so that’s the ‘stealth’ box ticked as well.

The aviation-inspired case and engine of Horological Machine No. 4 – first launched in 2010 – are one. This 2013 ‘Final Edition’ case blends high-tech titanium for its lightweight and strength with a sapphire centre section offering a view into the engine. Black PVD provides the titanium with its shadowy cloak of concealment without blocking the light playing off the contrasting matte and highly polished surfaces.

The HM4 engine is the culmination of three long years of development. Each of the 300-plus components – including the regulator and even the screws – was developed specifically for this anarchistic calibre. Horizontally configured dual mainspring barrels drive two vertical gear trains, transferring power to the twin pods indicating hours/minutes and power reserve.

But describing HM4′s engine through its mechanical functionality is like describing Renoir’s work through the chemical composition of his paint. Only careful contemplation enables full appreciation, and the sapphire case section and display panels top and bottom allow full access to the flawless fine finishing of HM4′s intricate and vibrant micro-mechanics.

The sleek aerodynamic form of HM4 has its roots in Maximilian Büsser’s childhood passion for assembling model plane kits, though none looked remotely as futuristic as these. The striking transparent sapphire section of the case requires over 185 hours of machining and polishing to transform an opaque solid block of crystal into a complex, exquisitely curved panel allowing the light to come in and the beauty of the HM4 engine to stand out. Every component and form has a technical purpose; nothing is superfluous and every line and curve is in poetic harmony. Articulated lugs ensure supreme comfort. Highly legible time is a fringe benefit.

HM4 Final Edition is an elusive limited edition of just eight pieces. It closes the book on the HM4 series, which was limited to only 100 movements over all models.

Horological Machine No4 Final Edition

Inspiration and Realisation

A long childhood passion for assembling model aircraft had Maximilian Büsser’s walls, cupboards and ceiling covered in small aircraft of every description. Planes were what he saw last thing at night and then again first thing each morning. Many boys sketch supercars and fast planes, but few have the drive and determination to make their dreams come true. Büsser created MB&F to do just that. HM4 was born of the child’s fantasy and the man’s tenacity.


HM4′s engine was entirely designed and developed by MB&F over three years of intensive work. Each of the 311 components was developed specifically; no off-the-shelf components could be used due to the extreme nature of its architecture.

Two mainspring barrels connected in parallel provide 72 hours of energy and they transfer their power to the dual jet-turbine-like indication pods via vertical gear trains. Visible through a shaped sapphire display panel on the top of the case, a distinctive streamlined cock supports the balance, its centre cut away to reveal as much of the oscillating wheel as possible and validating the « kinetic » in MB&F’s « kinetic art ».

A work of art rewards when viewed from different angles and Horological Machine No4 is no exception. Turning the machine over reveals a panorama of meticulously finished micro-engineering through the sapphire sections. In a playful trompe l’oeil, what at first glance appears to be a micro-rotor in the form of MB&F’s iconic battle-axe is actually a bridge.


For a timepiece not developed specifically to tell the time, HM4 performs that role superbly. In fact, with its highly legible dials perpendicular to the wearer’s wrist, Horological Machine No4 might be described as the perfect pilot’s or driver’s watch.

On the left pod, the power reserve is clearly indicated by a skeletonised hand echoing MB&F’s battle-axe motif. On the right, hours and minutes are displayed by bold, arrow-tipped Super-LumiNova filled hands. The two aviation instrument-styled instrument indications are directly controlled by their own crown: one to wind/re-fuel the tanks, the other to set the time.


Inspired by aviation, the case of HM4 imparts speed, power, technology and refinement in equal measure. Visually, the case is composed of three parts: two streamlined jet-turbine-styled pods supported by a horizontal section housing the engine, which is clearly visible through transparent sapphire display panels and the central section of the case itself. Technically there are also three main sections, which include the dials and articulated front lugs; a central section in sapphire offering unprecedented 360° access to the superbly finished engine; and an aft section tapering down to the dual crowns.

More than 185 hours of intricate machining and meticulous polishing are required to turn an opaque solid block of sapphire crystal into the clear, light-filled atrium of the central case section, which reveals part of the HM4 engine and engineering details.

The contrasts of matte with highly polished surfaces under the black PVD, stealthy straight lines with seductive curves, and rigid forms with articulated arms, sets HM4 Final Edition apart from anything visible (or not) on land, sea, or air!

Technical Specifications
HM4 Final Edition is a limited edition of 8 pieces in blackened titanium


  • Three-dimensional horological engine developed 100% by MB&F
  • Manual winding with two mainspring barrels in parallel
  • Power reserve: 72 hours
  • Balance frequency: 21,600bph/3Hz
  • Number of components: 311
  • Number of jewels: 50


  • Hours, minutes and power reserve indicator
  • Hours and minutes on right dial, power reserve indicator on left dial
  • Separate crowns for time setting and winding


  • Grade 5 titanium coated with black PVD
  • Dimensions: 54mm wide x 52mm long x 24mm high
  • Number of components: 67
  • Articulation of lugs: 3°

Sapphire crystals:

  • Five sapphire crystals: 2 x dials, 1 x central case section, 2 x display panels (top and bottom)

Strap & Buckle:

  • Hand-stitched calfskin strap with titanium/white gold custom-designed folding buckle attached to articulated lugs