The ETA 2837 is a hi-beat movement from the 1970s, designed to be a chronometer. It's quite rare today, and only found in vintage watches. Hi-beat in general is super rare, currently only sold in the Zenith El Primero and Grand Seiko line.
According to Dan Fock:
Around this time companies were experimenting with Hi-Beat movements, 36,000BPH. The more beats the smoother the movement and the more accurate. The 2837 is a Chonometre grade movement. Based on the very robust 2824 family, but significantly upgraded.
- Skeleton page
- According to Otto Frei it shares some parts with the ETA 2824, so it's probably the same base ebauche.