There is a certain type of helmet that is very common in viking age reenactment. It either has a simple hemispherical or conical spangenhelm construction with an attached nasal. However there is no archeological evidence i am aware of for these helmet types from the viking age, although they are shown in some of the artwork from that time:
[ Linked Image ]
Leiden macabees, dated to the 10th century

The fallen helmets on the ground seem to have a nasal attached to them, but interestingly none of the helmets that are being worn show them.

Then there is the helmet that is known as the "Thames" helmet, although it might be from northern france:
[ Linked Image ]
dated to the 11th century.

This wouldn't really fall under the spangenhelm classification, since there are no bands keeping the plates together, but instead they are riveted to each other. Helmets of this type seem to be depicted in the Leiden macabees, suggesting that helmets of this type were in use from the first half of the 10th century. However this is not the type of helmet i am talking about, as there are no bands holding the plates together.

And here is an example of the type of modern reproduction helmet, that reenactors often wear:
[ Linked Image ]

To be clear, I think that many of these types of reproduction helmets are good interpretations, but as there are no surviving originals there are bound to be some errors. There are surviving helmets that have a similar construction to the helmets shown in some of the viking age artwork, but they are from an earlier period, and often lack nasals (And the ones that do have a nasal are quite elaborate, and don't resemble the helmet types in question.)

So what are your thoughts on this subject?

here are the links

http://manuscriptminiatures.com/4887/14192/

http://www.reenactment.de/reenactment_start/r...guide.html

The "Thames" helmet has been discussed in an older forum post

https://myArmoury.com/talk/viewtopic.php?p=208562

I would love to read some discussion about this as well. The lack of surviving examples can be maddening.

This discussion from 2011 does have some good thoughts and links, in case you haven't seen it.
https://myArmoury.com/talk/viewtopic.php?t=24773&postdays=0&postorder=asc&start=0