Hi Martin,
Thank you for sharing those. I've always wondered about the specific functioning of the hands of the 1/100 model, can you tell me more about it? The short, centrally-mounted hand, what happens to it once it passes the 10? Have you seen a user manual for the 89 series? I recently got my first Seiko stopwatch, an 88 series 1/10 sec. I don't know how much they share with the 89 series (having troubles finding an 89 tech guide), but below is a shot under the dial of the 8800D movement. I'm pretty sure it was never serviced before; the excess, somewhat sloppy lubrication on the chronograph parts from the factory was interesting to see:
Not to go off track too much, but I wonder if the 89 series has the same rubber bumper on the end of the second-setting lever? It comes against the fourth wheel teeth when the stopwatch is in the "stop" and "reset" conditions, and over the years mine had an impression of the teeth molded into the rubber:
This was causing slight issues with errant stopping/starting (just by a few tenths of a second), but flipping the bumper around on its post solved the problem. For this reason, I'd advise the 88 series stopwatches to be left in the "start" condition when not in use.