check that HALKI postmark is not the greek one is the turkey one where the Halki Theological School is now.
Thank you Manosp, indeed.
HALKI (Island) HEYBELIADA, One of the Prince Islands, in the sea of Marmara.
I read the Catalogue incorrectly, I noted Island, and picked the wrong one.
Later CDS Pmks had HALKI (ILE)