Robert Greubel and Stephen Forsey spent four years bringing their first invention to fruition.
A 60-second carriage rotates inside a four-minute carriage measuring 15mm in diameter. The former is inclined 30° to the latter. It contains a variable inertia balance and balance spring with a Phillips curve. The two carriages comprise 128 components and have a combined weight of 1.17 g. The 30° inclination of the smaller carriage's rotation axis in relation to the rotational speed of the two carriages allows the balance wheel to permanently oscillate in all positions.