But, nine months after his death, surprises are still emerging from the jaw-dropping house once owned by the quiet, unassuming retired economist with a canny eye and a raging passion for art.

His will include a bequest to the National Gallery of Australia of 19 works that together are worth $8 million, making it one of the most significant private bequests from a collector in the gallery's history.

The works, which include two paintings by John Olsen, a piece from Arthur Boyd's ground-breaking Brides series, a late incarnation of Ned Kelly by Sidney Nolan and two drawings by Brett Whiteley, are just a taste of the 900-strong collection amassed by Mr Boxer over five decades.

They were selected after careful consultation with curators in the early 2000s, and many years as an active volunteer guide, to complement and fill gaps in the gallery's own collection.

The NGA's senior curator of Australian painting and sculpture Deborah Hart, who visited Mr Boxer at his home several times since the early 1990s, said this was typical of Mr Boxer's approach to his collection, and to the art world in general.

"He was really on the ball in terms of what was happening in the contemporary scene," she said.

"And there were major purchases - they were not small works. I guess if you were tentatively dipping your toes into the field of collecting, you might go for a small Boyd or a small Olsen, but in fact he went for really major works. So what that says to me is that from an early stage, he really was a serious collector. It wasn't just something to decorate the house, it was something that was saying, 'I'm going to make a commitment to Australian art and I'm going to do it through the people that seem to be the best'."

And he had a curator's eye for disparate works that hung well together, whether on his living room wall, his bathroom cupboards, the oven door or the walls of the National Gallery.

"One of the things that strikes me in seeing the group of works together is that they are quite diverse, but they are of that period of modernism ... they're not sedate works by any means," she said.

"But when you see them together, somehow it all works, it all clicks together."

The NGA's announcement comes a day after Mr Boxer's significant indigenous art collection was auctioned in Melbourne, a sell-out event that fetched more than $1 million.

Co-executor of his estate Kristian Pithie, who ran the Chapman Gallery selling Australian Indigenous art in Manuka for several years, said Mr Boxer, a bachelor who lived modestly and left no immediate family, had been one of his most discerning clients.

He regularly stopped by the gallery for hours at a time to talk about art and see the latest exhibition.

Although he often bemoaned the lack of space in his house, he was captivated by the latest developments in the indigenous art scene, and always managed to find a place for a new piece.

"A true collector always has room for another work," Mr Pithie said, adding that Mr Boxer never bought on impulse.

"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."

And he was not one to hoard his possessions jealously; he often brought fellow guides and art enthusiasts back to see his collection, and readily loaned works to exhibitions throughout Australia.

And now, as per his dying wish, Australian art-lovers will have the chance to experience part of the joy he must have felt every time he stepped inside his own front door.