Having worked at Goodwill for three years, Maria Rivera knows to set aside items that might be of value when sorting through stacks of donations. But she didn’t know a painting she plucked from a pile could be worth about $12,000.

Rivera came across the painting, which depicts an elderly woman drinking tea, while sorting through recently donated items at the Goodwill retail and donation center in Manassas. The painting was later found to be an original by late-19th century Italian artist Giovanni Battista Torriglia.

“We take into consideration the quality of the painting,” Rivera said of knowing whether to set the artwork aside.

Brendan Hurley, chief marketing officer of Goodwill of Greater Washington, said the process is arbitrary.

“When merchandise is donated, our production managers are instructed to set aside anything that they think might be of substantial value,” Hurley said.

Those items are then passed on to Goodwill’s e-commerce office, where they are researched and, if found to have value, put up for auction on shopgoodwill.com.

The painting was initially put up for auction on the site, Hurley said.

“We originally posted it online, not really understanding its value,” Hurley said. “We felt concern for our bidders and our own reputation, and we thought that it would be best to pull it offline and get it authenticated.”

Hurley took the painting to Murphy Kuhnert, a Georgetown art consulting firm, late last month.

“It’s quite common for people not to know what they have,” owner Amy Murphy Kuhnert said. “It’s important for everyone to do research.”

Kuhnert, who has owned her consulting firm for five years, said this was the first piece she’d seen brought to her from a thrift store. The actual value of the Torriglia piece will be whatever it sells for at auction, Kuhnert said, but she estimates the value to be about $12,000.

“That number comes from examining the works of Torriglia that have sold at other auctions and looking at how this particular painting compares to his other work,” Kuhnert said.

The painting was put up for auction officially at 6 p.m. Wednesday on shopgoodwill.com. As of Friday evening, bids were at $4,505. Bidding for the painting ends Wednesday.

“We’d love to generate at least $8,000,” Hurley said. “This unique opportunity is rare so we’re hoping to generate as much revenue as possible to help make our mission possible.”

Proceeds will go to Goodwill Industries International to provide employment and resources to people with disabilities, Hurley said.

“Goodwill has done a wonderful job of representing whoever donated the piece,” Kuhnert said. “Proceeds of the painting will really go to a good cause.”