The so-called 'Notitia dignitatum' is a compilation of 78 lists, interspersed with 89 pictures, which was ultimately copied from an original compilation that was created, or last edited from its sources, between A.D. 395 and 425.
Students of the administrative and military organisation of the Roman state in the late 4th century consider this document immensely valuable as an indispensable supplementary source for understanding many, often less detailed, references that are contained in other documents and inscriptions.
But apart from its value as a supplementary source, the 'Notitia' preserves much information that is unavailable elsewhere. It indicates the titles and ranks of a considerable number of administrators and commanders who are unknown from other sources. It alone preserves lists of many of the estates and treasuries of the imperial private and public revenue and of factories and arsenals. It contains lists of the administrative departments or offices of the empire, both central and provincial, together with the titles of the more important members of the imperial civil service and of the palace secretariat. It also indicates the titles and ranks of both central and provincial commanders of the imperial military service, the names of units and types of units of the army and navy, and the place-names of their garrison sites, in lists whose comprehensive nature is unparalleled by any other known and extant written sources for the history of the Roman state.
Above copied from the extensive website on this document (original codex lost) as it exists in various copies. See this website for much, much more:
http://members.ozemail.com.au/~igmaier/notitia.htm