JLC 859 is a chronograph movement from Jaeger-LeCoultre.
Introduced in the Reverso Gran'Sport Chronograph in 2002, the calibre 859 features a back-to-back design as in the Reverso Duoface. But in this case, the reverse houses a retrograde chronograph movement, descended fro the JLC 829 found in the limited-edition Reverso Chronograph Rétrograde.