In her discussion, Pferdehirt followed RMD V, and wondered if the medallions of Severus from 207 were relevant, and they do seem to show a different (‘official’?) pattern, which presents a second problem. Severus had not used IMP numbers after IMP XI on his coinage for ten years after 198, but we have IMP XI still attested on rare medallions of 207 and 208, and there is also now a new piece for Severus, unfortunately undated, with IMP XII: 207 IMP XI/TR P XV COS III (IOVI VICTORI; Jupiter in quadriga attacking giants (Fig. 15) 208 IMP XI/TR P XVI COS III (PROF AVGG); Emperors on horseback and soldiers (Fig. 16) ? IMP XII/[ ] ([ ]AVGG); togate Emperors holding small victory with 6 attendants (Fig. 17) We also have two, otherwise undated, medallions for Caracalla as IMP II: ? IMP II/ADLOCVTIO AVGG; two Emperors with prefect addressing soldiers, one with horse ? IMP II/CONCORDIAE AVGG; two Emperors in military dress sacrificing over altar; behind, two Victories Regarding the new medallion for Severus as IMP XII, Clay comments: ‘the obv. a little tooled, but I am confident that the legend including IMP XII is correct. Rev. worn and undated (AVGG in ex. is all that survives of the legend), but date must be between 208 (when he was still IMP XI on the PROF AVGG medallion) and mid 210 (not yet BRIT). Caracalla’s two IMP II medallions, though both unfortunately with undated reverses, seem to belong to the same period. On Gn. Pl. 95.2 Caracalla is without beard, so date should be earlier than mid 209, when his full beard appears. Rev. ADLOCVTIO AVGG, a type that appears with dated legends on sestertii of all three emperors in 210. On Gn. Pl. 95.3 Caracalla might be bearded (hard to be sure), and rev. is CONCORDIAE AVGG, two emperors sacrificing, each crowned by a Victory, a type which similarly appears on sestertii in 210. Both of these medallions are without BRIT, so before mid 210. And both apparently after 208, since IMP II is not added to Caracalla’s obv. legend on Gn. Pl. 95.4 of 207 and Pl. 95.5 of 208. So according to the coins, Septimius became IMP XI and Caracalla IMP in Jan. 198; then Septimius became IMP XII and Caracalla IMP II c. 208-9. This latter acclamation presumably occurred before Geta became Augustus in late 209, since I think there is no evidence that Geta ever became IMP II. And IMP II was the last acclamation accepted by Caracalla during Septimius’ reign, since he was still IMP II on his sestertii of early in 213, BMC pl. 75.2-4 and 6. We can deduce that Septimius too, on the official reckoning followed by the coins, was still IMP XII when he died. I’m not sure what to make of the diplomas you cite naming Caracalla already IMP II by March 207!’ Clay later wrote: ‘I had an idea about the possible occasion of IMP XII = II on the coins. Septimius had made Caracalla IMP and AVG, and Geta Caesar, on the occasion of his own IMP XI for the capture of Ctesiphon early in 198. So maybe he made Geta IMP and AVG on the occasion of his own IMP XII and Caracalla’s IMP II? Those acclamations would then have occurred late in 209, when Geta apparently became Augustus, judging from the scarcity of his coins dated just TR P = 209. Septimius’ IMP XII medallion and Caracalla’s two IMP II medallions would belong to 1 Jan. 210, fitting with the fact that Caracalla’s two rev. types were also used on sestertii of 210. Septimius’ medallion depicts two emperors shaking hands (or holding a Victory on globe?) in the presence of other figures, probably a commemoration of the IMP XII = II victory and/or of Geta’s promotion to IMP and AVG. A problem for this reconstruction, however, is the beardlessness of at least one of Caracalla’s IMP II obv. dies, which might suggest that he was already IMP II on 1 Jan. 209 (accepting my argument from their titulature that virtually all second- and third-century bronze medallions were apparently struck for use as New Year’s presents). The occasion of this hypothetical acclamation for all three emperors late in 209 would presumably have been the success of Septimius’ invasion of Scotland, which according to Dio “forced the Britons to come to terms, on the condition that they should abandon a large part of their territory”. Septimius would have modestly declined the title BRIT on this occasion, only accepting it in the course of 210, maybe for a preliminary success in his attempt to quell the ensuing rebellion of the Maeatae, against whom he sent a punitive expedition according to Dio.’ I am wondering how this proposed chronology will fit with that suggested by S. Elliott in his book entitled Septimius Severus in Scotland, mentioned in another Coin Talk thread by Jamesicus.