I can see where that Wikipedia illustration came from: it is taken from the plaquette made for Grand-Duchess Joséphine-Charlotte as Dame (Knight) in the Order of the Seraphim.
It is no fantasy Arms but the personal "small arms" of Joséphine-Charlotte, is the one without the Seraphim Order's cordon.
Oval arms ( it is a female spouse )
Quarter I of Nassau
Quarters II and III of Brabant/Belgium
Quarter IV of Luxembourg
Bedecked with an "open crown" (without velvet) = a grand ducal crown. (The Dutch use the same open crown as Luxembourg (a grand-ducal crown) because apparently King Willem I thougth it was aesthetically more pleasing than a closed crown with red velvet.)
The King's Standard in Belgium, with a five "closed crowns" (= with a red velvet hat)
The King's Standard in the Netherlands, with an "open crown" (no velvet hat) - actually a grand-ducal crown
This is heraldically incorrect for a King and actually there are two existing royal crowns, clearly with a velvet cap. Here is the one used during the Investiture in 2013: http://www.lichtpunt.nl/upload/afbee...ldigd/loo5.jpg
But when King Willem I said in 1815: "I want an open crown on my heraldic Arms!" who dared to disagree?