"Seiko planned to take on the Swiss at their own game. So rather than a modular, disposable plastic movement, the 7a series had a proper, quasi-decorated 15 jewel metal movement that could be regulated, disassembled and repaired. It even has a very traditional finger damper spring on the centre seconds pinion. Seiko really threw investment, thinking and effort into this one. This explains why, despite often impressive abuse, so many survive.
Notice those little rectangular plates over parts of the movement? Each of those protects a tiny stepper motor – one for each of the chronograph functions. And that’s what this watch is all about. Press the button at 2 o’clock and the chrono starts. Instead of a blizzard of flickering digits, the centre seconds ticks off the seconds one at a time while the 1/10ths dial zips round. In fact, it’s moving at 1/20th second intervals. The minutes total up over at the 9 o’clock subdial and there’s a running seconds at 6 o’clock.
https://wornandwound.com/seiko-7a28-pt-2-quiet-beauty/