In 1973 the owners of trucking company F.H. Stephens purchased a painting by Jeffrey Smart, Radial Road, from a Melbourne gallery. The couple paid $3750 for the canvas, which the famous painter had produced the year before.

In the Stephens' possession for more than four decades, the existence and whereabouts of the artwork remained virtually unknown. Then, earlier this year, Sotheby’s received a call – the widowed wife, who had later remarried, was ready to sell the piece.

At the end of August the 1972 painting goes on the block, and Sotheby’s estimates it will sell for between $500,000 and $700,000.

“It’s very exciting to be involved in reintroducing a spectacular composition back into Smart’s oeuvre,” says Geoffrey Smith, chairman of Sotheby’s Australia.

The rediscovered artwork incorporates all the hallmarks of a great Smart painting, says Smith. He saw the work for the very first time earlier this year. Smart is known for his meticulously painted and geometrically precise urban panoramas, where the materials of industry and transport are often the focus.

Radial Road depicts a highway – a typical subject for Smart – at a curve in the road. The backs of three trucks are painted, one behind the other, as they drive towards an expanse of high-rise apartment blocks. A solitary figure in a pink dress stands on the road, watching the lorries pass by.

The Stephens were not dedicated art collectors and at the time of purchase, though Smart was well known, he had by no means achieved the level of critical acclaim or celebrity that distinguishes him today. The family owned a transport and shipping company, and for them the composition simply struck a chord.

In the case of Radial Road, no reproduction of the image existed before now. So while the title itself existed in various records of Smart's oeuvre, what it actually was, and looked like, was a mystery. There’s a catalogue from a 1973 show at which the painting was on display, but the booklet doesn’t include an image of every piece in the exhibition, only their titles and measurements.

Apart from this, the title Radial Road is also referred to in a 1983 book on Smart, which contains a comprehensive list of the works he produced during his lifetime.

“Once we had this information we went to Smart’s archivist, Stephen Rogers,” Smith says. “He came back and confirmed that it was this very painting.”

For Smith, the rediscovery of this particular painting is meaningful because of where it sits in the timeline of Smart’s output. Radial Road is the direct precursor to Smart’s famous Truck and Trailer Approaching a City from 1973, says Smith. And the bold red lorry in those paintings also appears in a work painted between 1979 and 1980 called The Guiding Spheres II (Homage to Cezanne).

“You put the three of them in a row – it’s the same truck,” Smith says. “You get the story, the lineage of how Jeffrey Smart’s iconography developed and changed.”

Radial Road will be on display at Sotheby’s in Melbourne August 14–17 and Sydney August 21–26.