This MB&F Horological Machine 4 Thunderbolt Titanium & Sapphire is rated 9.6 out of 10. It comes with box and paper dated in January 2016. The HM4 was designed to look like two engines, mounted on their sides, with a structure design to allow them to sit on a person’s wrist. It is estimated that less than a hundred pieces of HM4 variations were made by Max Busser and his team, this piece is highly collectible and extremely rare. A modern day horological art piece.