Calibre JLC 170
Calibre 170 was a special competition movement from Jaeger-LeCoultre, and was their first-ever tourbillon movement.
First built in 1946, Cal. 170 was a large (49.72 mm diameter) movement used in chronometer competitions. It was housed in a plain pocket watch case, and just 26 were made between 1946 and 1954.
It was not until the 1993 introduction of Cal. 828 that Jaeger-LeCoultre would sell a tourbillon-powered watch to the public.