From:
John Leach's Encyclopedia of Postal Authorities :

W

Wadhwan - Württemberg

Wadhwan - Württemberg

Wadhwan
Wake Island
Wales
Wallachia
Wallis & Futuna Islands
Walvis Bay
Wenden
West Berlin
West Germany
West Irian
West New Guinea
West Ukraine
Western Army
Western Australia
Western Command Area
Western Samoa
Western Thrace
Western Thrace (Greek Occupation)
White Russia
Windward Islands
Wolmaransstad
World Health Organisation
World Intellectual Property Organisation
World Meteorological Organisation
Wrangel Government
Württemberg
Württemberg (French Zone)