The 7750 is probably the dominant mechanical chronograph movement right now. Designed by Valjoux, a company now part of ETA, it's known for good performance, durability & decent price. It's a coulisse (cam) design, as opposed to the more expensive column wheel.
Visually, it's damned ugly, especially compared to the hand-wound movements like the Venus 175, but hey, few people care.
Check out the shape of the rotor - although buyers can change it, they often don't bother, so that's the fastest way to recognize the movement. This one is actually from my Chinese chrono:
- Debut 1974
- Size 30mm, 13.25 ligne, 7.9mm thick.
- 25 jewels, Diafix I think
- Automatic, unidirectional winding
- Rate: 21,600 or 28,000 vph
- Power reserve: Appx 40 hours
- Hour, minute, central seconds, quickset day and date. Complications available include annual calendar, moonphase and more.
- Accuracy rating varies with grade, available with chronometer certification.
- Undecorated and unadjusted
- Awesome in-depth review by Walt Odets
- Swisslab flash page Awesome - teardown and rebuild instructions.
- Wikipedia page
- TZ discussion of descendants
- Discussion, opinion and more - excellent page.
- Comparison of sixteen movements
Perspective and opinion
The 7750 certainly has some drawbacks (unidirectional winding, the jump when engaging due to the tilting pinion instead of a vertical clutch, the famous rotor wobble, plastic bits here and there, etc) but it's dominant and ubiquitous. For something nicer, see the Piguet 1185, Venus 175, or Seiko 6S37.