Some background. During Diocletian's reign, he instituted a plethora of Empire-changing policies to not only raise the Empire out of the crisis of the third century once and for all, but also allow it to prosper once again. One of these changes was a reformation of the currency. The debased antoninianus (augmented by Aurelian, and his successors) was replaced by the 10g follis and the currency was re-valued in an attempt to bring economic stability to the Empire. Although the standard did not last long before debasement started all over again, it does provide us with an array of beautiful coins to study from all over the Empire as a large supply of the new standard coins were needed for use by the populace. I counted 14 mints in operation that provided this supply. Last year, while travelling in the UK, I visited a museum in London which had a beautiful display of Ancient Roman coins on a map. I was so inspired that I wanted to do the same for this collecting theme. So here's the museum's display, and mine is below. The coins from north to south starting with my favorite : The first one is a gem from @jamesicus's collection. An early issue follis from the newly liberated diocese of Britannia. Diocletian AE Follis 296 A.D., London Mint, null Officina 9.06g, 28.0mm, 6H Obverse: IMP C DIOCLETIANVS P F AVG, Laureate, truncated, bare neck bust right Reverse: GENIO POPV–LI ROMANI, Genius standing, facing left, head surmounted by a modius, naked except for chlamys over left shoulder, holding patera in right hand and cornucopia in left arm Exergue: -/-//LON Provenance: Ex. Ancient & Medieval Coins Canada Auction 1, Lot 128, Ex. James Pickering Romano-Britannic Collection Reference: RIC VI Londinium 1a, Cloke & Toone 1.01.001 (R) Maximian AE Follis 295 A.D., Treveri Mint, 2nd Officina 10.55g, 27.0mm, 12H Obverse: IMP MAXIMIANVS AVG, Laureate head of Maximianus to right Reverse: GENIO POP-VLI ROMANI, The Genius of the Roman people, nude but for chlamys Exergue: B/-//TR Provenance: Ex. Leu Numismatik Web Auction 10, Lot 1515, Ex. Tetrarchy Collection Reference: RIC VI Treveri 154b The following is an example of the invasion folles that Constantius took with him to supply the to-be-liberated Britannia with the new standard of coinage. These coins were likely minted by Lugdunum mint workers (evidence from style similarities), thus I attribute it to Lugdunum. Constantius I Chlorus AE Follis 294 - 296 A.D., Lugdunum Mint, null Officina 11.15g, 28.5mm, 6H Obverse: FL VAL CONSTANTIVS NOB C, Head of Constantius Chlorus, laureate, right Reverse: GENIO POPV–LI ROMANI, Genius standing, facing left, head surmounted by a modius, naked except for chlamys over left shoulder, holding patera in right hand and cornucopia in left arm Exergue: -/-//- Provenance: Ex. eBay 2019 Reference: RIC VI Lugdunum 17a Constantius I Chlorus AE Follis 303 - 305 A.D., Rome Mint, null Officina 9.287g, 30.3mm, 6H Obverse: CONSTANTIVS NOB CAES, Head of Constantius Chlorus, laureate, right Reverse: SAC MON VRB AVGG ET CAESS NN, Moneta, draped, standing left, holding scales in right hand and cornucopiae in left hand Exergue: -/-//R(crescent)T Provenance: Ex. Forum Ancient Coins 2019 Reference: RIC VI Rome 112a Constantius I Chlorus AE Follis 296 - 297 A.D., Heraclea Mint, 1st Officina 8.39g, 29.0mm, 12H Obverse: FL VAL CONSTANTIVS NOB CAES, Head of Constantius Chlorus, laureate, right Reverse: GENIO POPV-L-I ROMANI, Genius, wearing modius, nude, chlamys draped over left shoulder, standing left, pouring liquid from patera in right hand and holding cornucopiae in left hand Exergue: -/-//HTA Provenance: Ex. Budges-Beak eBay 2019 Reference: RIC VI Heraclea 18a Maximian AE Follis 298 A.D., Antioch Mint, 6th Officina 8.75g, 27.0mm, 6H Obverse: IMP C M A MAXIMIANVS P F AVG, Head of Maximian, laureate, right Reverse: GENIO POPV-L-I ROMANI, Genius, wearing modius, nude, chlamys draped over left shoulder, standing left, pouring liquid from patera in right hand and holding cornucopiae in left hand Exergue: (✱ on ✱)/(crescent on ς)//ANT Provenance: Ex. Dattari Collection, Ex. Jesus Vico Online Auction 5, Lot 211 Reference: RIC VI Antioch 50b Constantius I Chlorus AE Follis 299 - 303 A.D., Carthage Mint, null Officina 9.75g, 28.5mm, 12H Obverse: CONSTANTIVS NOB CAES, Head of Constantius Chlorus, laureate, right Reverse: SALVIS AVGG ET CAESS FEL KART, Carthage, wearing long robe, standing front, head left, holding fruits in both hands Exergue: -/-//Γ Provenance: Ex. CNG Electronic Auction 456, Lot 751 (part of) Reference: RIC VI Carthage 32a Diocletian AE Follis Alexandria Mint (not yet attributed) Thanks for looking, all! Please post coins of the 1st Tetrarchy from all the mints. I would be keen to see examples from mints that I have yet to get examples from: Ticinum, Aquileia, Siscia, Thessalonika, Cyzicus, and Nicomedia.