And no one could have guessed that its occupant, a gentle, unremarkable retired senior public servant, was an incredibly canny collector with an abiding passion for contemporary Australian art.

Alan Boxer, who died last June at the age of 86, was an economist and academic who began a private art collection when living in Melbourne in the early 1960s.

He quickly developed a taste and an eye for modern contemporaries such as Albert Tucker, Fred Williams and Arthur Boyd, and later Brett Whiteley and John Olsen.

He moved to Canberra in 1975 to take up a senior role in Treasury, and his collection grew over the years to include a vast number of works by Indigenous artists.

This was sparked largely by a visit to the Chapman Gallery in Canberra, run by the late Judith Behan, in 1988, when, as he put it, he became "hooked" on Aboriginal art.

His close friendship with the gallery continued after Mrs Behan's death, and Kristian Pithie took over in 2007; he continue to regularly stop by the gallery for hours at a time, to talk about art and peruse the latest exhibition.

By the time he died, leaving no immediate family, his house was full to bursting with more than 900 works of art.

However the paintings and objects were not crammed in a jumble, but carefully curated and displayed on every available surface in the house – including on cupboards and the oven door – as well as leaning against pieces of furniture and on the stairs.

Mr Pithie, who is co-executor of his estate, said Mr Boxer often bemoaned the lack of space at his house.

"One thing that he would always say to me is, 'My house is full – I'm not going to buy another work'. But a true collector always has room for another work," he said.

He said Mr Boxer never bought a work on impulse, but often deliberated for days or weeks at a time, pondering how it would fit in with the rest of his collection.

"One could never be accused of coercing him into buying the work because he was very cognisant about what would fit into his collection," he said.

"And even if it was the most beautiful work, at the cheapest price or whatever, if it didn't work he wouldn't take it."

This week, Mr Boxer's indigenous collection – 179 works – is set to go under the hammer at Mossgreen Auctions in Melbourne – an event that has private collectors and public galleries alike buzzing with excitement.

Mossgreen's head of Indigenous Australian art D'lan Davidson said the collection was an exceptional one, not least because it had stayed in the one place for so long.

"That's also an important part for us because it means that the collection hasn't been disbanded at all, its strengths are still in place," he said.

"He didn't just get a painting because he needed a painting by an artist – he waited for the right work, and as an auctioneer … I can be selective in what I take, but if you get this sort of quality across the board, it makes my job so exciting."

He said while the works were of high quality, they had been priced conservatively, and many private collectors would be interested.

Nonetheless, a few of the works, such as an eye-catching large-scale canvas by Emily Kame Kngwarreye, priced at between $100,000 and $150,000, would have collecting institutions scrambling.

Mr Davidson said Mossgreen hoped the auction would fetch up to $800,000 or more, and a further announcement about other parts of the Boxer collection is expected this week.

But those who knew Mr Boxer say money never came into it.

He was not a wealthy man – a non-drinker, he lived alone in the same Weetangera house for the rest of his life, wore op-shop clothes and never splashed out on expensive cars or holidays – but spent his money carefully and lovingly.

He was also generous: after his retirement in 1986, he became one of the National Gallery of Australia's first volunteer guides, and was known to invite other guides to his house to view his own collection and talk about art.

He also readily loaned paintings and drawings to exhibitions throughout Australia.

Mr Pithie said Mr Boxer was an art lover above all else.

"The thing about Alan is that he was deeply passionate and deeply committed to the art world, and interested in it," he said.

"He was almost like someone who knew he couldn't be part of the art world, so he did what he could do best, which was to support galleries and support artists by buying the works."

The Alan Boxer Collection of Australian Indigenous Art will be auctioned in Melbourne on Tuesday, March 17, at 6.30pm.