Moving away from Naval matters,
I attach a page showing use of APO SX 3 in Salonika, 17 February 1916. One sees often use of APO SX 3 from May 1916 on wards on Lemnos serving 3rd Battalion R Marines and other Garrison troops.
This is the only example I record showing earlier use of this office in Salonika, as write up shows, there is no mention in the War Diary DDPS Salonika for an opening / closing of this office.
A very scare usage.
Chris