The ETA 2783, which debuted around 1974, is a direct relative of the caliber family of the ETA 2824.
The biggest difference between them is in the escapement works: The 2783 beats only with 21600 instead of 28800 A/h and does not use an ETAChron fine regulator.
According to the desired version, the hairspring length is regulated either by a long regulator arm or directly on the hairspring.
As usual on ETA movements of that time, a click wheel changing mechanism is used; the rotor of the ETA 2783 is, unlike to that of the ETA 2824, only axle and not ball-beared.
The rotor drives both wheels, but the click wheel mechanism assures, that only one of both is in use, while the other one spins free. So, in whatever direction the rotor turns, the mainspring is always wound in the same direction.
ETA selfwinding movements always wind in both directions, this was always the case, starting from the first ETA selfwinding movements in the fifties and it hasn't changed until now.
Another feature is, that the click wheels decouple the rotor and spin very fast when the watch is hand wound. This solution does not make a very worthy appeal, but it always worked and still works reliably.
The construction of the watch works is the same modern one, ETA established in the sixties:
The center second hand is directly, the minute wheel (at position "5") indirectly driven. This construction allowes a very large balance and mainspring, achieving best precision and long duration.
On the dial side, there's the date indication mechanism, which advances the date in a slow manner, but can be quickset in the center crown position.