What is this suppressor thread?

Very seldom use silencers. New 22LR rifle has a little takedown cleanable Hushpower IV which I will not use - will sell on. Can someone identify this thread - is it a 1/2 x 20 or 1/2 x 28 etc.. Standard Hushpower (Guncity) thread. One pic is mm, the other inches:

Attachment 179656

Attachment 179657

Thanks Mike

Its a 1/2-20

Thanks for that :)