Sotheby’s Australia is poised to stage one of its biggest indigenous auctions after scrapping its $5000 lower threshold.

The move has given Sotheby’s competitors reason to smile after they predicted the brand would go downmarket when it was bought by Sydney auctioneer Tim Goodman from its US parent almost a year ago.

Sotheby’s might have the last laugh yet when it reveals today in Sydney almost 350 paintings and artefacts with an upper estimate of $6.21 million for its first Aboriginal and Oceanic art auction for the year.

The sale will be held over two days in Melbourne from July 26 but it will have to do exceptionally well to surpass the company’s record-setting 2007 Aboriginal art auction, which fetched $8.2m.

Sotheby’s head of Aboriginal art, Tim Klingender, said scrapping the threshold “was a business decision because it’s a great area of the market that it brings in new buyers who hopefully in time will turn into major collectors”.

This auction marks the end of an era for Mr Klingender, set to become a consultant with the company where he has worked for 20 years, 14 in his current role.

“We’re always extremely selective about what we include but we were offered a lot of great work from Australia and overseas,” he said.

Nine works from Joan and Peter Clemenger’s collection have been consigned and 10 from the Donald Kahn collection.

Gabrielle Pizzi’s legacy as a tastemaker in indigenous art is set to be tested when 23 lots from the late dealer’s personal collection go under the hammer.