Just five per cent of the Australian War Memorial's astonishing collection is on public display at any time.
The rest is stored away and available for public viewing on only one day each year. This Sunday, September 18, is the 2011 day.
On show for the first time at the memorial annexe in the Canberra suburb of Mitchell is the latest acquisition, a former RAAF Sabre jet fighter which saw operational service in Malaya and Thailand.
The jet was purchased from a New Zealand collector, who had hoped to restore it to flying condition.
For that reason it's in good shape, albeit with non-genuine US Air Force markings and Korean War colours.
The aircraft was manufactured by the Commonwealth Aircraft Corporation and delivered to the RAAF in January 1957.
It subsequently served at the Butterworth air base in Malaya during the period of confrontation with Indonesia and even at Ubon in Thailand during Australia's little-known commitment to a force providing security for US aircraft conducting missions over Vietnam.
The aircraft, tail number A94-954, was retired in 1971, then sold privately, moving to the US and then to New Zealand.
Although in good condition, there's still a major job ahead to restore its appearance while it was in RAAF service.
The memorial's senior curator John White said the jet had been flown by dozens of RAAF fighter pilots.
"We have been in contact with a few of them," Mr White said.
"They are very important for our work because they can flesh out the history for us."
Their log books record individual flights made by the aircraft.
"That's really the only place you can get that information," Mr White said.
So what would the memorial pay for such an item?
Because it was a private sale, Mr White isn't saying, other than that it was in the order of tens rather than hundreds of thousands of dollars and came with a wide range of spares and other parts.
"It was an extremely good deal for us," he said.
On display at Mitchell is all the big stuff not on show at the main memorial complex including tanks, vehicles, aircraft, guns and munitions.
That includes a Japanese Type 95 Ha-Go tank, a very significant item as it was one of two used by its forces at the 1942 Battle of Milne Bay.
The tank is undergoing a detailed and complex process of conservation which has revealed, among other things, scrawled names and service numbers of Australian soldiers and small-arms damage inflicted by Australian troops during the battle.
"One Australian soldier was decorated for hitting this vehicle with what's called a Boys anti-tank rifle," Mr White said.
"There's still a hole in the driver's vision visor which you can see." http://creativecommons.org/licenses/by/3.0/legalcode