parma

[caiusbeerquitius]

Addition:

The tombstone of the signifer Quintus Luccius Faustus from Mainz, 1st c. AD, shows a dished shield from 3/4 backside view. horizontal grip, no info about the umbo. The shieldlooks like a smaller version of the 3rd c. AD shields from Dura. If it in fact was smaller may be discussed, since it quite often happens, that shields are displayed way smaller than the findings suggest they actually were.
this is not visible here in the database, but if you see it in nature, or if you look at the photo in Junkelmann´s "Die Legionen des Augustus", Taf. 33, you will probably agree.

Same for Caius Valerius Secundus:


Gnaeus Musius seems to have had a (smaller?) version of the republican scutum:



Unknown 3rd c. AD standard bearer from chesters carries a Whatthehellisthat? - type shield. (Also known as shield-type QXZ-348-a):





The 200 AD tombstone of the cornicen Aurelius Bitus and his son Vitalis depicts Bitus with a round or oval shield hanging on his left side. Size for the small version of a shield would be from the shoulder to the middle of the thigh (?). The shield may be flat or not (since we don´t see the umbo).

What we can say for sure so far, is that mostly (leave out the chesters standarbearer) cornicen´s or signifer´s shields were round and were hanging on their left side. I think it is hard to make a point about these shields being flat, but looking at Quintus Luccius Faustus and Caius Valerius Secundus from the first c. AD, at least two seem to have been dished.

That´s the information I can deduct from artistic evidence so far.