How does this artwork elucidate its Authenticity?
For more than 100 years, it was attributed to the "School of Porbus". It was not attributed to Rubens until after World War II. According to Brian Sewell, it is an "uncomfortable Rubens" and the attribution "doesn't quite ring true". A panel of academics employed by Christie's examined the portrait and ultimately concluded that the painting is a genuine Rubens.
Porbus Brian Sewell Christie's