Maximilian Busser & Friends (MB&F) has revealed his latest master timepiece, the Horological Machine No. 3 Frog, a whimsical twist on the HM3.

The time is displayed by two rotating domes underneath a pair of sapphire crystals that resemble a frog’s eyes.

The protruding eyes of the (amphibian) frog enable it to see in many directions without having to turn its head.

On the new HM3, the hour and minute indicators are raised domes that, like the frog, can give their owner a wider view of the time without having to twist a wrist.

The Frog differs substantially from HM3 in that it is the aluminum domes that rotate under the sapphire crystals in the Frog, whereas it is the hour and minute hands that rotate around their respective stationary cones on HM3.

Rotating domes of this size and shape posed MB&F with a number of technical challenges.

The hour and minute domes are machined from solid aluminium – chosen for its optimal strength to weight ratio.

The domes weigh in at just over 0.5g. They are milled first from the outside and then the inside to arrive at a paper-thin wall thickness of just 0.28 mm, which reduces their energy requirements to an absolute minimum.

Even the fabrication of the semi-spherical sapphire crystal domes was incredibly demanding and only recently even possible at all.

This is due to the fact that any slight imperfection in the sapphire might introduce a disconcerting magnification effect.

The sapphire has to be shaped and polished to be perfectly uniform.

The Frog’s unusual method of indicating time necessitated the development of a new gear train for the HM3 engine.

This was because the aluminum hour dome of the Frog rotates in 12 hours compared to the 24 hour revolution of the HM3 hour hand.

And as the oversized date wheel is driven from the hours, the gearing driving the date had to be reworked as well.

Only 32 Frogs will produced this year, 12 of which will be in a limited edition black titanium case with green rotor, while the remaining 20 will be standard titanium with a blue rotor.