I have often heard the statement that the "carolingian helmet" which bears a resemblance to the much later morion, derived from late roman or byzantine art, but I have yet to see any of those models that it is said to have derived from. However I myself too doubt whether the franks actually used this type of helmet.

Here are some pictures of these helmets:

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This first one is from the Bern Psychomachia, and clearly shows influences from antiquity, with pteryges and all, but quite interestingly it is also shown in manuscripts where the artist depicted contemporary equipment, (although with a much less flared brim.) :

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This is from the Psalterium Aureum, and seems to depict things that would be expected from the period, apart from the helmets ofcourse.

So this is quite a tricky one isn't it? If someone could point me to some analogies from roman or byzantine art, that would be very nice :D

Links:
http://manuscriptminiatures.com/4956/15039/
http://manuscriptminiatures.com/4957/15044/

Morion type with cheek guards. I believe 6th century.
http://www.tforum.info/forum//index.php?showtopic=37494

RomanArmyTalk has some examples:
https://www.romanarmytalk.com/rat/thread-22589-page-2.html

Arch of Constantine:
https://upload.wikimedia.org/wikipedia/commons/e/ee/Arch_of_Constantine_-_detail_3_%284293299626%29.jpg

You might want to check out this FB page. The guy that runs it had a replica of something similar made.

https://www.facebook.com/Francia-orientalis-163657917158184/

Thanks for the links. Perhaps they copied these helmets from late roman artwork and manuscripts to show themselves to be the continuation of the western roman empire, that they were thought to be at that time.

It should be noted that these helmets appear most commonly in themes related to the Psychomachia (Battle of spirits or soul war) perhaps indicating that the carolingians copied some roman manuscripts (or perhaps copies of roman manuscripts) of the psychomachia wich featured these kinds of helmets

It is notable too, that even long after the carolingian period, these helmets still appear in relation to psychomachia in artwork, such as this example from notre dame, depicting mercy facing off avarice, dated to the 12th century:

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This might indicate that they copied the carolingian copies to get a "roman feel" to their art.