Incredible that there is absolutely no consultation between the various museums or auction houses and museums.
recently a historically important long lost helmet was auctioned as part of 3/4 field armour , which belongs to a suit of armour of Gilbert de Saint Hilaire in the Heeresgeschichtliches Museum in Vienna.
Even more remarkable is that absolutely nothing of above in the description can be found.
The new owner found himself in possession of a an extremely lucky hit, as important pieces like this are never offered in the arms & armour market.
please see
http://www.vikingsword.com/vb/showthread.php?t=21081
best,
Jasper