Many medieval accounts attest to the ability of mail to provide excellent protection against all sorts of weapons. Anna Commena of Byzantium describes the mail of Norman mercenaries as "arrow proof" and goes on to say that it "made them almost, if not completely invulnerable."
But a good amount of the surviving mail I've seen (mostly 15th century and later) seems too lightly constructed to provided the immense level of protection often described. In a lot of cases the rings look worn down with age and corrosion, but by how much I can't say.
Here is an interesting look at a (presumably) 13th century coif found in good condition, and the rings seem to be of substantial construction.
http://forums.armourarchive.org/phpBB3/viewto...ilit=+coif
Are thicker rings like this a common trait in earlier mail?

I don't think time period is as important as what was also being worn. You tend to see heavier types of mail when it is worn by itself. It tends to be lighter when it is layered with other types of armour. It just happens that mail was more often worn by itself in earlier periods.

Dan,

What is this based on? Is there actually hard evidence for this? I thought something for years like that and never could find any real support. There is no doubt a wide variety of mail types. And some like the secret mail shirts and some mail collars show patterns where there is a clear design/make quality that is repeated that gives an idea that this mail was clearly done in a very specific manner but I am still looking for something that proves mail worn with other armours was different than those worn alone. None of the art, text or remaining armours give me that impression.

RPM

I have nothing to back it up except for secondary sources. I'd love to see hard data too.

Dan,

I feel the same way. I started looking on my own and I started to really wonder where the evidence was. We have loads of mail remains, many textual accounts, tons of it in art but I just am seeing so little hard evidence for a system that uses different mail under plate for example or with padding that I am quickly starting to wonder if there is any substance to it. Sort of like the idea gothic armours with fluting did so to make strong but thinner/lighter armour or the same with heat treatment. There is no real backing but I hear all these and other statements fairly often.

Well I guess we just have to keep looking and see where the evidence goes.

RPM