Did Roman cavalry wear face-masks in battle?

[caiusbeerquitius]

and the flimsiness of face-mask helmets. They are all about spectacle and little to do with combat, as the vestigial neckguards make abundantly clear.

Just briefly, again:
The flimsiness: The metallurgical analyses made for these kinds of objects show quite the opposite. See
F. Willer, R. Meyers, Herstellungstechnische Untersuchungen der eisernen Gesichtshelme aus Nijmegen, in: R. Meyers, F. Willer (eds.) Hinter der silbernen Maske, Nijmegen 2007, p. 31-50.
I. Joosten, R. Meyers, F. Willer, Die metallurgische Untersuchung des Eisens der Gesichtsmaske Kat. Nr. 2, in: R. Meyers, F. Willer (eds.) Hinter der silbernen Maske, Nijmegen 2007, p. 57.60.
E. Geiß, F. Willer, Experimentelle Archäologie: Schmiedeexperimente zu den Gesichtsmasken aus Nijmegen, in: R. Meyers, F. Willer (eds.) Hinter der silbernen Maske, Nijmegen 2007, p.61-68.
R. Meyers, H.-J. Schalles, F. Willer, Schussexperimente mit einer rekonstruierten römischen Torsionswaffe auf definierte Metallbleche, in: R. Meyers, F. Willer (eds.) Hinter der silbernen Maske, Nijmegen 2007, p. 69-76.

We know that the helmets were made exactly to measure of the wearer, see Herstellungstechnische Untersuchungen... p. 34.

The weight or thickness alone of the objects cannot be an argument pro or contra wearing them in battle, just as the level of decoration cannot be this. And should we then not first find out how thick (better: stable) such a helmet needs to be for a Roman cavalryman? The thickness of a metal does not exclusively tell how stable it is. Form and composition are just as much important. (Form: If you play WOT you know what I mean... ^^)

Short neck guards: Hm. That would be so, if we base this on the assumption that there is a need for larger neck guards on horseback in battle than in Cavalry Sports. Do we know that this is the case? Aren´t large neckguards actually bad when on horseback? when you fall of your horse backwards you may be very happy about a short neck guard, I suppose.

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I still think it is not so sensible to try to establish a normative here. Wearing or wearing these not in battle may have varied from time to time (e.g. before or after Arrian), from unit to unit (Thracian Cavalry vs. Bracaraugustan) or from place to place (Syria vs. Britain). It is impossible to prove that they were exclusively worn in the hippica gymnasia, I think, likewise it is impossible to prove that they were worn in battle alone (a case which none makes, I think). Probably the truth lies, like so often, somewhere in the middle. As Junkelmann shows, one can also make some very good points for the use of these objects in battle.

At that, I do also not see the necessity to establish a normative. I think a teleological approach is bad, though. The sources should be investigated from a rather subjective point of view. What should not be done is to have a fix idea and then to approach the sources in terms of proving one´s idea. That´s a methodological no-go, I learned in History class.