Late Roman Attic helmets

[Nathan Ross]

Perhaps, like the gypsum casts seen in 19th century art schools, any artist had some models of ancient arms and armour for use in military scenes

Quite possibly. But I think this tends to be assumed rather too often. The two scenes above are quite interesting - the first is straightforward mythology/religion: Mars is not intended to look like a 'real' soldier, and his helmet is suitably old-fashioned. The second, I think, show the wounded Aeneas, so again it's mythology. The equipment and dress, though, looks a lot more detailed and less generic - the figure on the right appears to be wearing either a Persian cap or some kind of helmet padding! Perhaps it's stuff from the artist's dressing-up box, but it could well be an attempt at accuracy. Of what, however, is another question..

In the case of some of the tombstone reliefs show above in the thread, I suspect there's less likelihood of merely generic depiction. Look at the armour of the two soldiers in the Mikkalus relief - the artist has gone to some trouble to carve those distinctive belts, and the shape of the two different helmets (although why the soldier on the left is holding another identical helmet I can't decide - unless he's about to hand it to the mounted Mikkalus?)