When was the Niederbieber Helmet put out of use?

[Nathan Ross]

when did the Roman Army stop using the Niederbieber Helmet?

Fragments of the skull reinforcement of Niederbieber-type helmets were found at Dura Europos in Syria, dating to the destruction of c.AD257. The very latest known example of the type might be the helmet, possibly unfinished, from the fort at Rainau Buch, which was abandoned c.AD260.

We have little to no evidence for Roman helmets between 260 and c.300, when the earliest composite 'ridge' types start appearing. There was a rumour of an example from Poitiers dating to around 270, but that turned out to be a gladiatorial helmet, I believe!