Official Roman coins from about the 4th century onwards show clear mintmarks
indicating the city where the coin was minted, also often the officina
(workshop) that minted the coin.
Also there were many local mints. Most cities in the East and many in the West, especially in Spain, minted local coins. In the West this ended with Caligula, in the East local mints continued their activity till way into the 3rd century.
Many variations are known.
Official Roman Mints with most common mintmarks, many variations of these marks are known. Please note that some mints like Colonia Agrippina do not present any mint marks
Some examples of official Roman mints with fotos below:
Antiochia, 5th officin, ANTE
Arleate (Arles), A R KONOB
Colonia Agrippina, (Köln in Germany), no specific mintmark, but
Victorinus is thought to have minted this coin at this city
Heraclea, H, HER
Kyzikus, M K Delta
Mediolanum, M D COM
MD PS = "Pure Silver" from Mediolanum
Ravenna, R V COMOB
Rome, R M COMOB
Rotomagus, known for this type under Carausius
Thessalonica, 5th officina, SMTSE (Sacra Moneta TS E)
TES for Thessalonica
Treveri, TROB (pure Gold from Trier, Germany)
TR = Trier