Frank,
Note: Originally primarily used in Muscat these issues have often been listed under that name in catalogues. Other variants of the country heading in catalogues include: "Muscat and Eastern Arabian Agencies", "Muscat and Dubai and Arabian Gulf Agencies", or (eg in some American listings) "Oman". The current designation in the UK is "British Postal Agencies in Eastern Arabia", since it more accurately reflects the wide usage in Muscat (1948-1966), Qatar (1950-1957), Abu Dhabi (1960-1964), Dubai (1948-1961).
http://www.gbos.org.uk/index.php/Country_List/8