Ten years ago, TAG Heuer unveiled its Monaco V4 Concept Watch, which was the world's first watch to incorporate belt drives, linear mass and ball bearings. In 2009, the watchmaker released the production version, simply called the Monaco V4. At Baselworld 2014, we recently spied the latest incarnation, the Monaco V4 Tourbillon. It's reportedly the first watch to ever feature a belt-drive tourbillon complication.

Like its predecessors, this watch features a V-shaped main plate on which the movement's four barrels are mounted at an angle to one another, looking "like the cylinders in a Formula One motor-racing engine." It also still has the form factor of the iconic TAG Heuer Monaco watch worn by Steve McQueen, in the 1971 movie Le Mans.

What's different this time around is the fact that its transmission belts, which are no thicker than a human hair, have been incorporated into a tourbillon complication.

As explained by TAG Heuer, "a tourbillon is a mechanical system for regulating the speed at which a watch beats." While this is usually done by placing the balance wheel and escapement within a rotating cage, the Monaco V4 Tourbillon's unique arrangement apparently eliminates backlash on the tourbillon, resulting in "the absolute fluidity of its rotation."

Other stand-out features include a black titanium and sapphire case, an automatic linear rewinding system, a mass that's guided by a linear railroad as opposed to the traditional rotating system, and barrels that are held and rotated on ball bearings.

You can see the inner workings of the Monaco V4 Tourbillon in the video below. The watch should be available later this year, priced at 150,000 Swiss francs (about US$169,600).

Source: TAG Heuer