H.R.Robinson Helmet Typology

[Paullus Scipio]

Christian wrote:

But, as such, I´d absolutely agree with a typology based on physical characteristica.

...and there's a problem right there.
There is much more to a Roman helmet typology than just appearance/style/physical characteristics, as R-R recognised and as I have been trying to point out here. Any typology based on just physical appearance is foolish, and overlooks important factors.
As Christian recognises, such a typology only works for a limited period from Caesar's day to the third century or so onward at best, and yet still does not cover everything. Such a limited typology, which could be overthrown by the next find, is all but worthless. :roll:

As I said above, there is a working typology for the Greek, Hellenistic and Republican period. It could be better, but it works.

.....I would dispute this. For a start, such an assertion is based on the fact that there are fewer types/examples extant than for Imperial times, and is simply untrue anyway!
What is true is that until the primacy of Rome over Italy ( i.e. roughly the period of the second punic war, or immediately after), it is better to speak of "Italian" rather than "Roman" Helmet styles.
In short, you can't develop a typology without considering historical factors as well as physical, nor can you develop a 'system' based purely on, say, the first three centuries A.D. simply because that is where most of our present evidence is concentrated.