I have size 12 Fahys case that will need stem,sleeve
and crown (have plenty of those)the issue is that the case long neck got no threads how can I fix that case?
Is there special stem that goes into Fahys case?

Perhaps it's for watches like the Illinois "Extra-Thin" where the stem is part of the watch, like modern wristwatches?
Regards,
Bob

that make sense thanks Bob.

Peter I have a Fahy's Montauk 20 yr. I am pretty sure is a 12s.

If I can fix my camera I'll send pics.

It needs a bow and crystal, all other parts are there but I don't know if the crown is original.