"There's not a lot of paintings that come up for sale because he couldn't make enough paintings in his lifetime basically."
The last time Art+Object sold a Walters artwork was in 2013 for $430,000 and it has only ever sold one other black-and-white koru painting in 20 years.
"If it sells it would be a record price for Gordon Walters at auction."
Several collectors had expressed interest in the piece, but were "keeping their cards close to their chest".
The work, which measures 1220mm x 943mm, is one of 106 pieces being auctioned by Art+Object on Tuesday at 6.30pm.
Walters, one of New Zealand's most influential modern artists, died in 1995.
READ MORE:
• Colin McCahon's The Canoe Tainui sets record with $1,350,000 sale price
• Colin McCahon painting could fetch up to $2 million at auction