Evidence for legionary vs auxiliary helmet patterns

[jvrjenivs]

Is the current theory that a soldier could have any kind of helmet available by the armorers in his area, up to the amount that he could afford to pay?

No, I think there still is the believe that there is a difference in Cavalry and infantry helmets. But within the infantry helmets I think it's hard to tell which type each type of infantry (legionairy or auxilia) had used, if there is any distinction at all and a legionairy could just use what was available at the 'store', and within his budget.