"After van Eyck" is copy after Campin instead

Westport, from the USA, sells on 31 March 2019 in an interesting single owner (a lover of Pieter Brueghel) auction an "After van Eyck, possibly 16th / 17th century" oil on panel of a donor with Saint John, estimated at $2,000 to $3,000.

It is not a copy after Van Eyck, but after a 1438 work by Robert Campin, a portrait of Heinrich von Werl, professor of theology in Cologne. The original is (together with the other wing of the triptych) kept in the Prado in Madrid. It is remarkable, that while the work for sale follows the original in nearly every detail (things like the nail above the mirror, the view through the window, or the clasp on the book that carries the lamb), it totally omits the blue cloth in the center. I don't know whether this says something about how the Campin looked at some point in the past, or whether it is an unlikely error by the copiist, or if it means that the artist was poor and blue too costly?

The figure of Saint John here seems to have been the inspiration for the same saint in the Donne Triptych by Memling, nearly 50 years later (now in the National Gallery).

The work for sale is hard to date. A 17th century copy after Campin would be very late (though not impossible, I have once discussed an 18th century Memling copy), so it is more likely to be either 16th century or early 20th century. If it really is old, it should be easily worth the estimate even though it isn't painted very well, as it is a rare surviving example of the lasting infuence of Campin next to Van Eyck and Van der Weyden.

UPDATE: sold for $1,100 only.