Simon Marmion? Burgundian portrait

At Sworders, English auction house, they sell on 16 June an "After Jean Malouel (Flemish c. 1365-1415)" portrait of Philippe le Hardi (Philips the Bold) of Burgundy, estimated at £400 to £600.

The question is of course how long after Malouel this was painted. This is a well-known portrait for which the original is lost, but a number of copies are known, most famously one in the Dijon Museum (on loan from the Louvre). The one for sale here is of much lower quality, but has an inscription identifying the sitter as added bonus.

On the painting and on the back, the copy for sale is identified as by Simon Marmion (1425-1489). In the 19th and early 20th century, many primitive French paintings were attributed to Marmion, as one of the few well-known 15th century painters, and with no definitive paintings by him to fix his style once and for all. As he worked for the Burgundian court, a (copy of) a portrait of a Burgundian ruler was a logical candidate to be attributed to him. However, the quality of this copy is much too low to be by Marmion, and it looks more like an anonymous, provincial work. It could well be very old though, and if it is 15th or early 16th century, it should really be worth more than the estimate, more like £2,000 or thereabouts, due to the age and the identity of the sitter, not so much because of purely artistic value. UPDATE: as expected, sold for £3,100 instead of estimated £400!