Late Roman AE coins of the mid fourth century and later commonly have obverse legend which begins with the title "DN" for "Dominus Noster" ("Our Lord"). I wrote an educational web page which discusses the initial issues which use that title for the emperor. http://augustuscoins.com/ed/tetrarchy/DN.html Minted by Constantine for Maximian during his second reign, but before Constantine recognized Maximian as an active Augustus. 27-26 mm. 7.98 grams. This is the first AE type to use "DN" after the retirement issues of Diocletian and Maximian. DN MAXIMIANO PF S AVG [DN and S for "Senior" circled in purple] Domino Nostro ... Pio Felici Seniori AVGgusto "For our lord Maximian, religious/pious and lucky/fortunate senior Augustus" Struck c. 307 at Lugdunum (Lyons) by Constantine for Maximian (in time interval (3) below). GENIO POPVLI ROMANI, Genius standing. altar to left, N in field right, PLC in exergue. RIC VI Lugdunum 206 "c. Spring 307". This issue includes coins of Constantine and Maximinus II as Caesars and Galerius as Augustus. The title "DN" was initiated in 305 and became the usual title in 348. In between some coins have it and many don't. Can you show us a coin from before the FEL TEMP REPARTIO reform of 348 with the title "DN"?