The Jeambrun 23C is one of the last french cylinder movements and was made probably in the 1940ies. With its brige shape and the stripes decoration is appears quite modern, but technically it was already out of date, when it was made.
Even when the Jeambrun 23C was probably quite cheap at that time, its execution with a non-pillar construction and bearing rubies for balance and escapement wheel weren't usual for low-end movements at that time.
The gear train is typical for a cylinder movement: The non shock-protected annular balance beats slowly with 18000 A/h, and its cylinder controls the flat cylinder wheel with its sharp teeth, which is located beyond an own cock.
That wheel are following fourth wheel (for the subseconds indication a "6 o'clock"), second wheel and the center minute wheel, all directly driven.
The advantage of a cylinder movement over a lever movement is, that not only one critical part (the lever) is saved, but due to the much larger fourth wheel, one transmission step less is used, so there's no need for a third wheel.
The disadvantage (and the reason, why those movements are obsolet) ist, that the precision is pretty bad since the sharp teeth of the cylinder wheel always stay in contact with the metal cylinder of the balance, preventing the balance from swinging freely. And additionally, this construction is very prone to magnetism.
On the dial side, there's only a rocking bar winding mechanism with a very simple ratchet, which consists only of a spring, that intervenes directly with the teeth of the mainspring barrel.