Jacob Willemsz. Delff it ain't, but you do get an early William I of Orange (William the Silent) portrait

Pook and Pook, from the USA, sells on 22 April 2016 a Dutch portrait of a gentleman, dated 1582, and estimated at $400 to $700.

It has an old attribution on the frame for Jacob Willemsz. Delff, a Dutch portrait painter of the period, but the quality of the painting is not sufficient to maintain that attribution (larger image make the difference in quality more obvious).

It turns out to be a copy after a work by or from the circle of Dirck Barendsz, a portrait of Willem I of Orange, first Prince of the Netherlands, better known as William the Silent. It is kept in the Rijksmuseum.

The original was until now tentatively dated 1583, so perhaps through this copy we get a definitive date for it?

Without the identity of the sitter, the painting would be worth the estimate. With the royal connection, and assuming it is from roughly the same date (and not e.g. 18th century), it should be worth closer to $2,000 perhaps.

UPDATE: sold for $2,880.