Google the term glass frogs and you will learn about the Centrolenidae family of amphibians that have transparent abdominal skin so you can see the internal organs.

From today, MB&F will also be hoping the search engine finds its latest Horological Machine No.3 (MH3) the FrogX, which is presented in a sapphire crystal case.

It is a decade since MB&F made its first HM3 Frog, and the X is its most ambitious evolution to date.

The transparent cases provides uninterrupted views of the Megawind movement with its extended rotor, which is based on a Girard-Perregaux calibre that has been turned upside down to allow for an uninterrupted view of the enlarged 22ct gold and titanium winding rotor and the oscillations of the balance wheel.

The watch tells the time with two aluminium hours and minutes domes rotating under markers designed to resemble the lateral pupils of a frog’s eyes.

Machining the 48.3 x 52.7 x 17.5mm sapphire crystal case is a considerable challenge, particularly since the separate sapphire domes not only need to be uniform in size, they must also be exactly uniform and consistent in thickness and curve so as not to create any final optical distortions in the reading of the time.

There are three limited editions of the HM3 FrogX 10th anniversary watch being made, with just 10 of each made with blue, purple or turquoise rotors and matching colors of Super-LumiNova and case gaskets.

They are sold on matching colored leather straps.