This Cartier baguette-shaped watch with a sliding ("coulissante") cover concealing the dial, is powered by a Jaeger-LeCoultre Duoplan caliber.
credit: @alexstevensvintage
The
Jaeger-LeCoultre Duoplan is a family of
four calibres taking normal-sized watch parts, and
stacking them in
two layers (duo-plan), allowing the movement to be made much
narrower.

The
balance and
escapement have their
own layer, which is positioned
over the top of the
rest of the movement organised on
another layer.

- Cal. 101 – 6’’’ (14 x 4.8 x 3.4 mm). Produced from 1929 to present day
- Cal. 104 – aka Cal. 7BF, 7’’’ (16 x 5.8 x 3.4 mm). Produced from 1926–1959
- Cal. 403 – aka Cal. 9BF, 9’’’ (20 x 8.5 x 3.73 mm). Produced from 1926–1966
- Cal. 409 – aka Cal. 11BF, 11’’’ (23 x 10.5 x 4 mm). Produced from 1929–1962
credit: The Watch Club London, Time and Watches & Revolution
Thanks for reading.
Best, Emmanuel