Looks like a week or 2 at least left..
See if it's still putting pistils out in a week, and of course check the trics with a jewellers loupe.
Looks like its got to fatten up yet so I'd say 2 weeks at least.
you have a jewellers loop 60x?
or try to guess when the hairs are all mostly red brown rusty coloured and not sticking up anymore, kinda like they curl up into/on the bud..
if that’s your only choice than show us before harvesting..