Auxilia shields what options are there?

[Praefectusclassis]

I think the shield Adrian to which Adrian refers is the grave altar CIL VI 2177=ILS 2196 = Speidel, Denkmäler der Kaiserreiter 83. On the side of that altar is a shield with a pattern that looks sort of like the one above and has been connected to scene XCVII of Trajan's column. Speidel emphatically denies that they are the same, however. Interestingly, Speidel seems to suggest that the design on TC actually does occur elsewhere. But where?
This guy is actually not a Batavian, but instead possibly a custos armorum, belonging to the Equites Singulares Augusti serving in the 2nd quarter of the 2nd century.