I specifically specified mechanical watches. You can even match plain quartz oscillators with new exotic mechanical escapements, such as one from Zenith Defy L

I specifically specified mechanical watches. You can even match plain quartz oscillators with new exotic mechanical escapements, such as one from Zenith Defy Lab. You can get temperature compensated quartz watches that run at 10 or 5 spy. Note that watches spend a lot of time above 30C. There's not much point in calibrating relative to an atomic signal in a watch unless you're already thermocompensated. It's arguable there's also no point unless you have hand correction tech (seen in some Casios and Citizens) too.