The website lists this crest as sold. I have found items on auction websites before, only to lose the information when the next lot is listed, so I aim to preserve the text here. The website lists...
"A German heraldic crest for a tournament Great helm, Zimier, in 14th-15th century style.
Formed as a Swan's head, accurately constructed of gesso and coarse fibre, probably jute, over a hardened sculpted leather core, the base hollowed for fitting the crown of the helmet skull, with pairs of lace-holes at the sides, painted white and heightened in grey, the base and the beak with traces of gilding over a red base coat, and in "aged " condition throughout.
H. : 37 cm - Wt. : 1095 g"
http://www.invaluable.com/auction-lot/cimier-heraldique-pour-grand-heaume-de-tournoi,-40-c-ee0776023c
Points to note
* The lower edge is gently scalloped.
* There are two lacing points on the lower side. They are spaced at a ratio of 1:2:1 for hole:space:hole. They are a little over one hole diameter above the bottom edge. It would be a reasonable conclusion to expect another pair of holes on the other side.
*Based on the image size and the described height, the holes are around one centimetre in diameter, and the base is near to 22 cm in diameter.
* the lower edge does not appear to have an internal dome/cap.
*The lower edge has a 3.5cm wide band of smooth finish - potentially a thicker leather band to provide rigid support.
* The eyes are sculpted, while the feather detail is entirely painted on.
* The neck, at it's narrowest point, is 6 cm diameter.
I am getting a better idea of how this crest is going to look.