Ataman AP16 silencer threads, what are they?

[Phil Russell]

Question please:
I have been asked to make a silencer adapter for the Ataman AP16 pistol but have no real information to work on other than a photo of the dedicated AP16 silencer and a commercial adapter which is out of stock and extremely expensive.
Does anyone know the thread size on the pistol muzzle? Crude measurements from the photo suggest it is not metric and could well be 1/2", maybe UNF from crude measurements or maybe it is M12 x 1.25 (M12fine?). Before committing I would dearly like to know the thread size of the muzzle or the little plug that goes into the muzzle. The other end of the adapter is no problem ... commercial ones are 1/2" UNF.

Can anyone help?
Thanks, cheers,
Phil