When an emperor died there was sometimes a time lag between when mints began issuing coins in the name of the new emperor and the time they actually had a good idea what he looked like. Sometimes the first issues of a new emperor had portraits a lot like the previous emperor. Here is an interesting example from the Kingdom of the Bosporus (in Crimea, on the north side of the Black Sea). They often put the king's portrait and name on the obverse of their coins. The reverse has an imperial portrait and the year of the kingdom, but not the imperial name. The "portraits" are poor so we usually identify which Roman emperor it is by the date on the coin. Electrum, 19 mm. 7.69 grams. A stater. MacDonald 551/4. Anokhin 628B. On this coin we can read ""of King Rhescuporis" (II) in Greek around his portrait and "H Φ" (= year 508, in Greek) and a trident below an imperial portrait. Can you guess who the emperor is? Scholars think the Bosporan era began in Autumn, 279 BC. MacDonald says, in the standard reference "An Introduction to the History and Coinage of the Kingdom of the Bosporus," the year began in October [p. 101]. To get AD dates when the Bosporan date is greater than 297, subtract 297 and the year begins late that fall and continues until the following fall. H Φ = 508 in Greek. 508-297 = 211. So the year of the coin is late 211 to late 212. Who was emperor then? Septimius Severus died Feb. 2, 211 in York, England. His sons Caracalla and Geta were then co-emperors. Geta was killed by Caracalla in the closing days of 211 and Caracalla lived until 217. So the date of this coin is at least 6 months after the death of Severus. News traveled slowly compared to today and the Kingdom of the Borporus was far away from York, but there was time enough for such important news to make it all the way there. The imperial "portraits" in this series are cartoonish and rarely good enough in the third century to identify emperors merely by their portraits. There are some coins very like this one with this same date that have a "portrait" somewhat like Caracalla. They have his beard and scowl (see 551/1 in MacDonald), and all coins of this date have been attributed by scholars to Caracalla. On the other hand, this particular reverse image resembles Severus. The beard, with three points, is characteristic, even if artistry is lacking. Look at imperial denarii of Severus for comparison. The Bosporan mintworkers had the advantage of not having to name the emperor, so they could not be embarrassed by putting the the wrong portrait with a name; there was no name. Because so long had passed since Severus had died, it is likely this coin was minted after the mint knew that Caracalla was the new emperor (Geta was younger and less powerful), but did not yet know what he looked like. They used a portrait of Severus long enough to issue this coin. When they finally got a description of Caracalla, they switched portraits. There are other cases where the first issue of a new emperor uses a portrait much like the previous emperor. Can you show us an example?
One would think that since coins are often issued for the same ruler 'as caesar' and 'as augustus', this might not be a very common phenomenon.
below is a coin of Magnentius that looks a bit Constantinian. Perhaps this was intentional, though-- a bit of PR. Magnentius A.D. 350-3 22x24mm 5.0gm DN MAGNEN- TIVS P F AVG; diademed, draped, cuirassed bust right. FELICITAS REIPVBLICE; Emperor standing left holding Victory on globe in right hand and labarum. In ex. [F]PLG RIC VIII Lyons 109 here is the next issue, looking much more Magnentian Magnentius A.D. 350-3 22mm 5.3gm DN MAGNENTIVS P F AVG; rosette-diademed, draped, cuirassed bust right. FELICITAS REIPVBLICE; Emperor standing left holding Victory on globe in right hand and labarum. In ex. RPLG RIC VIII Lyons 112
When Maximinus Thrax murdered Alexander Severus, he took a while to make his way to Rome. In the meantime, celators had no idea what the new Emperor looked like, so the images on coins from this period kind of look a lot like an older Alexander Severus.
the Romans commissioned busts of the new emperors to be distributed to the cities in probably fairly expeditiously manner. I would expect that normally coins did not even need to be struck until the busts arrived and proper dies were then engraved.
For this early emission of Gallienus from the Rome mint, the celator still seems to have been doing Volusian. A Volusian (not mine) for comparison:
I was hoping someone would post a Gordian III with Balbinus features. I do not have one but CNG showed this one a decade ago: https://www.cngcoins.com/Coin.aspx?CoinID=91451 This is odd since there are coins of Gordian III as Caesar that are decidedly Gordian looking so the mint knew his face. One remotely possible answer (AKA guess) involves my theory that portraits may have been roughly cut by apprentices saving the time of the master cutters for finish work. This allows the mint to have a few dies in progress that were intended to be the heavier faced Balbinus that were completed as Gordian faces. I see the mint as doing anything they can to avoid trashing a die in which hours had been invested just because a ruler died. Recycling a die with legends might be more work than it would be worth but retouching a portrait in progress when the news arrived seems reasonable. In some cases we have a good explanation from the new man being out of town and no portrait bust was available to copy. Each case must be evaluated based on its own situation.
This engraver had no idea what Vespasian looked like. Vespasian AR Denarius, 3.22g Uncertain western mint, 69-71 AD RIC 1375 (R2), BMC 422, RSC 295a Obv: IMP CAESAR VESPASIANVS AVG; Head of Vespasian, laureate, r. Rev: PACIS EVENTVM; Bonus Eventus stg. l., with patera and poppy and corn ears A very early denarius struck for Vespasian at some unknown western mint. A similar Bonus Eventus was struck for Galba in Spain and the RIC speculates that an unknown Spanish mint may be responsible for this type too. This is one of the most unVespasian-like portraits ever minted with the heavy brow, long neck, and full head of hair.
Yet we have coins like my Maximinus Trax and others posted here that clearly show that in some cases celators had no idea what the new Emperor looked like and simply slightly modified the portrait of a previous Emperor. In the case of Maximinus Thrax I can see how it happened. Severus was murdered in the middle of a military campaign, and Maximinus would have been fairly busy for several weeks trying to wrap the military mess up and secure his position. I doubt he would have had much time to pose for any portraits or busts during that time, considering he had German tribes and former henchmen of Alexander Severus to deal with. His succession to power was fairly messy and he had to immediately and decisively deal with internal and external threats to his rule. In the meantime, you still had to send coins across the empire to pay the huge standing army and the equipment and supplies for the soldiers in the middle of a major military campaign. I doubt the mint could afford to shut down operations for a few weeks while waiting for Maximinus to finally get around to sitting for a bust, and then waiting the additional time for the bust to get from the wild frontier of Germany, across enemy lines, and all the way to Rome.
Here is a web site which discusses early and late portraits of Maximinus Thrax: http://esty.ancients.info/Maximinus/Maximinus.html As @Sallent notes, his early portraits resemble Severus Alexander. Maximinus Thrax Severus Alexander. Maximinus I / VICTORIA AVG Severus Alexander / SPES PVBLICA The legends, IMP <name> PIVS AVG, are the same except for the name, the hair is cut similarly, and the chin and beard are very similar. The nose is different, with the nose of Maximinus larger and humped and the nose of Alexander straight. The curvature at the top of the nose of Maximinus disappears in the second style and returns as a larger curve in the third. Scholars think the third style is the most accurate portrait: The earliest portrait of Maximinus looks more like Severus Alexander than it does the later portrait.
there is a theory that Maximinus Thrax suffered from acromegaly, which would account for his changing appearance on his coinage.
Maybe, but he was in power for a relatively short time, so his appearance couldn't have changed that drastically in such a short period. And certainly not from an Alexander Severus lookalike to what we know he looked like in his imperial busts.