A while back I won an auction: an Omega Speedmaster Reduced 39mm, ref. 3510.50.
The Speedmaster is one of those watches where you always know what’s powering it. The Moonwatch runs the hand-wound cal. 321 or the 861. But the Reduced — Omega’s attempt at a smaller, more everyday Speedy — runs the ETA / Valjoux 7750. Self-winding, vertical clutch chronograph, cal. 3220 in an Omega case. A lot of people treat that as a downgrade. I don’t, particularly. It’s honestly the coolest watch I’ve had the pleasure of holding, and one of my favorite watches I own.
What I wanted to understand was the movement and understand why, everywhere I read, it had changed watchmaking.
So I built an exploded view.
First, a brief history.
The 7750 was introduced in 1974 by ETA SA, designed by Franz Wyrsch. He replaced the column wheel typical of precision chronographs with a stamped switching cam — a more repeatable, manufacturable solution that traded some horological prestige for reliability at scale. At 28,800 vph and 25 jewels it became probably the most prolific chronograph movement ever made.
That same base movement, in modified form, powers the IWC Da Vinci Perpetual Calendar — ref. 3750, released in 1985, engineered by Kurt Klaus. The perpetual calendar module Klaus built accounts for the Gregorian leap year correction so precisely that the calendar is accurate to the year 2499. The only required manual adjustment falls on March 1, 2100 — when that year, divisible by 100 but not by 400, will not be a leap year, and the watch will add an extra day that shouldn’t be there.
The 7750 is what it is: a workhorse. But it’s also the foundation of one of the most mathematically careful complications ever put into production.
The interactive study I built covers all four subsystems: calendar and dial-side works, base movement and going train, the cam-and-lever chronograph, and the automatic winding module. Every part is procedurally generated — gear teeth, balance hairspring, rotor cutout — from watchmaking geometry rather than imported CAD. Source-informed rather than dimensionally exact, but accurate enough to teach.
The gear train animates at schematic speeds. The escapement pallet fork ticks at 4 Hz. The balance oscillates. The rotor counter-spins. Subsystems can be isolated, spread apart, or viewed in guided presets that move the camera to show each layer in context.
Enjoy, and let the time fly!