During World War II Australian men were called up for compulsory military service at 18 years of age and were classified as CMF (Citizen Military Forces) and allocated a regiment number with a letter prefix depending on their state of origin. They were unable to volunteer to join the Australian Imperial Force (AIF) until they were 19 years of age.
CMF units were not sent abroad except for countries neighbouring Australia (e.g. New Guinea and Bougainville), whereas AIF units were sent anywhere in the world. The 6, 7, 8 and 9 Division Units were AIF from formation in contrast to the 26 Battalion which was originally a CMF unit but when 75 percent of members became volunteers it changed to an AIF unit. However some members remained with the CMF and did not become volunteers during any part of their service. There was no favouritism, they did exactly the same as the volunteers, such as participating any actions the Unit was involved in, even to the extent of becoming a casualty.
AIF members had a colour patch with a grey background around the unit colours and wore "Australia" badges on both shoulders of their uniform. CMF members only wore Unit colours with no background and no "Australia" badges.
Letters in military regimental numbers:
V = Victoria
N = New South Wales
Q = Queensland
S = South Australia
W = Western Australia
T = Tasmania
D = Northern Australia (Darwin)
X = AIF (an Australian Imperial Force volunteer)