The painting, "Portrait of a Man, Half-Length," was for decades thought to be by an imitator or student of Frans Hals, the great Dutch painter often compared to Rembrandt for his vigorous, sometimes humorous depictions of the growing merchant class. Now Ben Hall, the head of Christie's Old Masters department in New York, is making the case that Taylor's painting was the handiwork of Hals himself. An expert in Hals' work agrees.

With the change in attribution comes a change in projected value: a canvas that would have likely brought less than $100,000 could now bring $1 million in an Old Masters auction in January.

The re-attribution is an example of the importance of seeing a painting, long known through reproduction, in the flesh. In the 1970s, the painting appeared in scholar Seymour Slive's catalogue raisonné on Hals — the industry standard for what is and is not authentic — as "doubtful and wrongly attributed." But Slive only saw the work in a black-and-white reproduction.

Hall, on the other hand, saw the painting in person in July, when it arrived at Christie's Rockefeller Center warehouse with other material from Taylor's estate. He said it "packed a real punch — making a tremendous impact from even 20 feet away."