Graham wrote:
If you have a selection of capacitors you could find the approximate value
empirically.

Most generic capacitors will show their max voltage rating as a DC value,
not an AC RMS value.
A 250V RMS capacitor should be replaced with at least a 400 volt DC rating.

My guess is the value is 0.1uF (same as 100nF)

Maybe the "10" just means +/- 10% tolerance


Great, those are a lot easier to find.

Cheers