It was nearly indestructible. Never left my wrist during daily jogs, showers, swims, saunas ... you name it.
After a few years finally some water had gotten into the housing. The watch was still working, but the screen had become less readable. Still, best watch ever owned.
Could be testable by turning the stopwatch on and then change the time. I have no idea how these clocks work; if they have a Unix time style counter as internal reference, then this test won't work. Would need a 36 bit memory to run for 20 years continuous counting; 30 billion times bit flipping on the lowest bit. Probably done differently.