Jervis Bay Territory

Jervis Bay Territory plate issued around 2010.
YZO-000 to YZO-999 were first reseved for the territory in 1995
It says ACT on the plate, but is not really part of ACT - only administered by ACT.  

Image from Jack McGee of Meridian, Idaho

"The Jervis Bay Territory is a territory of the Commonwealth of Australia. It was surrendered by the state of New South Wales to the Commonwealth Government in 1915[so that the Federal capital at Canberra would have "access to the sea".

It was administered by the Department of the Interior (and later by the Department of the Capital Territory) as if it were part of the Australian Capital Territory (ACT), although it has always been a separate Commonwealth territory. The perception that it is part of the ACT stems from the fact that under the terms of the Jervis Bay Territory Acceptance Act, the laws of the ACT apply to the Jervis Bay Territory.[10] In 1989, when the ACT achieved self-government, the Department of The Arts, Sport, The Environment, Tourism and Territories took over responsibility for the JBT's administration, and it has since been administered by various Commonwealth Departments responsible to the Minister for Territories." Information from Wikipedia.