Both. The Notitia is a confusing document, and it seems that the units represented in it were not always of equal status. So, you find shields that are different but from the same "regiment", and shields that are the same but from different "regiments". This seems to indicate a significant degree of merging and splitting of units in the time period that the Notitia was originally compiled. For instance, there is evidence that the elite guards of previous emperors would be posted to obscure frontier outposts by successive emperors to remove the chance of insurrection. Over time, these units would be divided up and sent to many small posts across the border limes.
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