In that year Gough Whitlam's Labor opposition spokesperson on Defence, George Gray, carried out a most extraordinary project the wildest imagination cannot dream of happening today.

Mr Gray personally designed a model of a new kind of heavy army contraption (part tank, part tank transport). Then as part of his pitch he showed it off (perhaps on the steps of what's now Old Parliament House) to the Holt government's Minister for the Army, Malcolm Fraser.

Hell will freeze before today's opposition defence spokesperson Stephen Conroy beavers away in his office at a similar project and then shows it off to an appreciative Minister for Defence, Marise Payne.

On Tuesday at Bruce Mr Gray's son Donald Gray, the custodian of this sturdy heirloom, shared this reporter's amazement at what had happened, then, in those olden days. Today the design of weapons systems is always thought of as a highly specialised task undertaken by sophisticated corporations (just think of our submarines, to be built by France's DCNS for $50 billion) not enthusiasts with zeal and spare time.

"Yes, it seems eccentric now, but that's looking at it with 21st century eyes. Things were much slower-paced in 1966," Donald Gray mused as we gathered in front of the contraption that starred, 50 years ago almost to the day, in front of Parliament House.

The Canberra Times quite rightly found it all newsworthy then and ran a story with a picture of the proud designer. With the model George Gray MP (an army veteran) provided a substantial essay of the invention's specifications and sterling qualities. He was convinced that Australia should brace itself for wars fought on Australian soil. He portrayed the made-in-Australia tank and its transport as a nimble system. It would be able to beetle from Alice Springs to our vulnerable far north, enabled to cover immense distances (up to 2350 miles) by virtue of having so much room aboard for 44-gallon drums of fuel.

The truly unique model vehicle (this is of course the only one ever made) has had severe tests of its sturdiness over the years. As a child Don Gray's little brother had been allowed to play with the heirloom, "as a toy", so that when Don Gray decided to restore it there was lots to do. Some parts were sourced "at great expense" from overseas.

The vehicle was never produced (Don Gray suspects that even if the government had found the design awesome, sheer partisanship would have prevented its adoption). But George Gray may, for ideological reasons, have knocked back a mighty customer for it.

"My father used to tell me," Don Gray reminisced on Wednesday, "that he was actually approached on the day [perhaps the 1966 public occasion The Canberra Times reported] by two guys from the Russian Embassy [seemingly very interested in the vehicle].

"Think about it! This was the height of the Cold War! They said 'Any chance you could pop over to the embassy?' but my father, who was very anti-communist, said 'Thank you very much, but no.' "