It’s interesting that the Roman Empire of Late Antiquity/Early Medieval period circa 400 AD, while not practicing personal heraldry, did practice military heraldry with shields permanently associated with military units and carried by the units’ soldiers. Here is an image from the Notitia Dignitatum first recorded and later copied over the years by monasteries:
Jeffry, thanks for this article. Roman civic and military symbols together with christian religious symbols and middle eastern symbols certainly influenced the development of heraldic charges (if not the heraldic system generally - which was something altogether innovative).
There are many resources available online for the Notitia Dignitatum. These include a complete order of battle of all Roman military units at the time: old legions stuck on the frontiers, newer "companion" units as well as palatine units. At least the palatine units and companions and some of the scholae units all had distinctive shields.
Even what are considered medieval titles such as Dux and Comes appear with regularity as military and civil bureaucratic offices.