British Offices Abroad
Offices abroad are sometimes dealt with on the detail page of the country where the office is located, sometimes on the page of the country operating the office and sometimes on a separate page such as this. The decision is a pragmatic one, largely based on the number of offices involved.
GB Offices in Turkey
|1st Aug 1885 Sc1 SG1||1905 Sc15 SG-L1|
Gibbons  lists stamps prefixed "Z" for a number of offices only
identifiable by cancellation from 1873 to 1904 before the 1885 surcharges
in Turkish currency run to 1914 (Sc1+, SG1-SG40).
Gibbons then lists issues in British currency overprinted "LEVANT" for 1905 to 1913 (Sc15+, SG-L1-L17).
Strangely, Gibbons then continues with more sections of "Z" cancellations, L surcharges and Turkish surcharges up to 1921.
Scott  lists them all rather more sensibly in date sequence from 1885-1921, numbered contiguously.
|Surcharges on GB stamps|
|40 paras on 2½ pence lilac||Sc101||1||1|
|80p on 5d green||Sc104||2||2|
|12 piastres on 2/6 lilac, bluish||Sc96||3||3|
GB Offices in China
Gibbons  lists more than a thousand GB and Hong Kong stamps used in China at British offices, identified by cancellation and then the first general issue on 1st January 1917 "to prevent currency speculation at the treaty ports".
The first set (1917-21) comprises 17 overprinted Hong Kong KGV stamps SG1-17 (Sc1-16) cent to $10 (wmk multiple crown CA).
The second set, 1922-27 with the same overprint, SG18-28 (Sc17-27), 1c to $2 had the multiple script CA wmk. Click the image to enlarge.