Introduced in 2004 in their Master Gyrotourbillon 1, this was the first appearance of the Jaeger-LeCoultre spherical tourbillon. It features two tourbillon carriages: The outer carriage rotates every sixty seconds and carries an inner carriage with the balance wheel, balance spring, and escapement. This inner carriage rotates every 24 seconds, completing 2.5 turns per minute, exposing the 14 karat gold balance wheel once per minute. The entire tourbillon mechanism consists of 90 parts yet weighs just 1/3 gram thanks to aluminum and titanium construction.
Calibre 177 is impressive beyond the 2-axis tourbillon, however. It is a Grande Complication with perpetual calendar, equation of time, and four retrograde hands. The 177 is an hand-winding movement made up of 679 pieces. It runs at 21,600 vph, has two barrels, 117 jewels, and a power reserve of 8 days.
This calibre was only ever used in the Jaeger-LeCoultre Master Gyrotourbillon 1.