The anonymous donation of a painting to Oxfam in Aberdeen could possibly net the charity more than £1,000.
An anonymous donor gave the painting to the Oxfam shop
The shop in Chapel Street received High Rise Neighbours, which shows depicts puffins and rabbits on a cliff.
It turned out to be by local wildlife painter Derek Robertson, whose work has raised hundreds of pounds at auction before.
A secret auction for the painting will now run for a week from Saturday, with a reserve price of £500.
The shop manager, Pamela Reid, said: "I knew when I looked at the painting that it was valuable but I didn't realise how much until I did some research.
"I would like to thank the anonymous donor for such a generous gift. By giving this painting to Oxfam we can raise funds that will help our projects throughout the world.
"It will be exhibited in the shop throughout the bid period for prospective buyers and art lovers to view."
Mr Robertson, who authenticated his work, said: "I am delighted that Oxfam is using my painting to support its work and I hope the auction is successful.
"I would ask anyone who has an interest in art or wildlife to pop by the shop and consider putting in a bid.
"I hope that I can meet the successful bidder when the painting is handed over."
Kathleen Leiper, owner of Riverside Gallery in Stonehaven, said: "Oxfam is very lucky to have Derek's work and his support.
"For the past few years he has been one of the artists we have regularly exhibited. His work is of tremendous interest. Oxfam has in its possession a painting of value.
"When High Rise Neighbours was sold at auction several years ago it fetched £900. I hope that Oxfam is equally successfully this time."