Calibre 878 is a watch movement from Jaeger-LeCoultre in the "Eight Days" family.
Like all of Jaeger-LeCoultre's "8 Days" movements, Calibre 878 uses dual barrels to power the movement for eight days. Unlike the Jaeger-LeCoultre Duomètre, however, these barrels are integrated into a single power source rather than being split among various complications. It is a hand-winding movement made up of 276 components, making it the most complicated of the family. Calibre 878 runs at 28,800 vph and has 35 jewels.
Calibre 878 was used in the Jaeger-LeCoultre Reverso Grande GMT.