At least, it is listed like that on Invaluable, the Isbilya website jumps from lot 18 to lot 20 without any explanation, so perhaps this is withdrawn?
Anyway, it is interesting enough to be discussed here even if it isn't for sale right now.
RKD. But the execution is harder, with brighter, more primary clours, more archaic use of gold, and an almost woodcut-like feeling.
Master of the Salem AltarI wonder if this isn't a German work, ca. 1480-1500 (so somewhat earlier than the auction catalogue suggested)? The pose of the figures, executed somewhat more childish than usual in early Flemish works (and foreshadowing the Antwerp Mannerism of some 20 yaers later) certainly points in that direction.
All in all, it is hard to pinpoint a region (though I would go for Germany, due to the woodcut-aspects), but the period seems to be late 15th century, more likely than the 16th century.
If it genuinely is a work of that period, it should be worth the estimate, as it looks to be in good condition.