What helmet is this? (please help :)

[ioannes sebald]

I must point out that i was not being critical of the rider,rather of those who should have noticed the"problem"from the outset,given some organisations views on accuracy and authenticity,i'll bet if i turned up at an event in 4th Century kit and donned an Imperial Gallic helmet then somebody would say something quickly enough,even if because i'd forgotten to bring my own.