"Introduction to Roman coins of the First Tetrarchy": http://augustuscoins.com/ed/tetrarchy/ which I announced here recently. That page is a place to begin if you want to learn about coinage during the reign of Diocletian and his co-rulers. The new pages are: a page about all the follis types of the First Tetrarchy http://augustuscoins.com/ed/tetrarchy/follistypes.html and page about SACRA MONETA folles: http://augustuscoins.com/ed/tetrarchy/SACRAMONETA.html (which is the second most common type). There were already several pages devoted to the GENIO POPVLI ROMANI type, which is by far the most common type: http://augustuscoins.com/ed/tetrarchy/Diocletianfolles.html Maximian, 286-305 "SACRA MONETA" type with Moneta standing left, holding balance and cornucopia. 28-26 mm. 9.91 grams. IMP MAXIMIANVS PF AVG SACRA MONETA AVGG ET CAESS NOSTR AQS RIC Aquileia 29b "c. 300" The tetrarchy had four rulers at once, making for interesting politics and coinage. Take a look at the main page: http://augustuscoins.com/ed/tetrarchy/ and see if you get interested!