Hi Lowkb,
Ron is right. I never thought of watches.
A 32 k/c crystal is about the best you will do
without spending a lot on some special item.
Getting 8 k/c from it will not be difficult.
I see Audioguru has it covered.
At those low frequencies you should take special care
with the rise times, dunno if the fall times matter so much,
and of course the interval of the pulse has to be short.
Maybe very short.
Depends what you're clocking with it.
Maybe some hand built digital converter .... ?
Best of luck with it, John