The TAG Heuer Monaco V4, first shown as a concept in 2004, is an automatic watch with an unusual movement. Instead of gears the movement uses belts to transmit power, and its four barrels are arranged like the cylinders of a V4 engine, with a linear weight that slides to wind the mainspring. The case follows the square Monaco shape, in platinum for the production version. I could not confirm every figure, such as case size, from a single source.

It was developed with the movement specialist Jean-Marc Wiederrecht and the concept was presented in 2004 before a limited production watch followed in 2009. A tourbillon version appeared later, in 2014, for the V4’s tenth anniversary.

Collectors see the Monaco V4 as one of TAG Heuer’s boldest experiments, and it was recognised at the Grand Prix d’Horlogerie de Genève in 2009. The original production watch was a limited edition and is no longer made, although later V4 variants have appeared.