The volume chronograph
The Valjoux 7750 launched in 1973 from the Valjoux division of ETA, designed by Edmond Capt in just 14 months. It became the volume Swiss automatic chronograph movement and remains so today, 50 years later. Used by Breitling Cal. 13 and Cal. 16, IWC Cal. 79320, Tag Heuer Cal. 16, Tudor 41 chronograph (pre-2017), Bremont, Hamilton, Tissot, Longines, Oris, and dozens more.
How it differs from premium chronographs
The 7750 uses cam-and-lever chronograph engagement (a cam profile decides when the chronograph engages or disengages), where premium chronographs use column-wheel (a stepped wheel that rotates between positions). Cam-and-lever is cheaper to manufacture and reliable; column-wheel is smoother to operate and finishing-friendly. The 7750's distinctive 'click' when starting/stopping the chronograph is the cam falling off the lever; column-wheel chronographs are smoother.
The 7750-derived family
The base 7750 has spawned variants: Cal. 7754 (GMT version), Cal. 7753 (different sub-dial layout), Cal. 7757 (small-seconds variant), Cal. 7758 (12-hour totaliser at 6). Brands modify the base 7750: Breitling adds rotor and balance changes for COSC certification; IWC adds Pellaton-modified winding; Tag Heuer adds extended power reserves. The architecture is so flexible that nearly every Swiss chronograph below CHF 15,000 is a 7750 variant.
When to recognise it
Sub-dial layout: 12-hour totaliser at 6, small running seconds at 9, 30-minute totaliser at 12. Date: at 3 o'clock. Distinct click when starting/stopping the chronograph. Day-of-week display: many 7750 variants have a day window (Cal. 7750-DD). If you see this layout on a Swiss chronograph CHF 2,000-8,000, it's almost certainly a 7750 derivative; the brand may dress up the rotor and bridges with finishing but the base is the 7750.