They may not have noticed it.
DOC is available for download from the publisher. Volume 1 Anastasius I to Maurice, 491-602 Volume 2 Phocas to Theodosius III, 602-717 Volume...
Lot of factors involved there, but there are plenty of specialists works. Talking about 3-4th century for example, if a coin is from Lyons, you...
Several books talk about stuff from the Codex Theodosianus check out Harl's Coinage in the Roman Economy and Hendy's Studies in the Byzantine...
Galerius was dead by the time these coins were issued, so none for him.
It's originally from the Codex Theodosianus https://en.wikipedia.org/wiki/Codex_Theodosianus
p.s.-- I think it is a wreath on the reverse instead of a shield
Separate names with a comma.