Back in 2018, MB&F introduced the Horological Machine N°9 — a unique timepiece honoring the Golden Era of automotive and aeronautic designs. Now, they're paying homage to the watch's intricate engine by re-releasing it with a completely transparent case. The in-house movement and dual spherical propellers are housed in a sapphire crystal shell that's held together by a three-dimensional gasket and a compound bonding process. Its vertical time display is also encased in sapphire crystal and features Super-LumiNova hands and markers. Available in four editions, including black, red gold, blue gold, and purple gold, each one limited to just five pieces.