I often see people trying to put together a collection from every Roman emperor, but how feasible is it to collect every Alexandrian (or) other eastern tetradrachms? Let's say we start from Augustus to Diocletian.
It's like other areas of collecting. Some coins are readily available, while others are scarce to very rare. The Alexandrian tetradrachms tend toward being comprised of billon from around Claudius forward, with progressive debasement. Strikes can be crude and the metal brittle and rough. Also the flans seem to shrink in diameter. If you are trying to assemble a type collection of Alexandrian tetradrachms by emperor, again, the scarcity or rarity depends on the emperor. You should be able to purchase a decent Nero tetradrachm with relative ease, while an Otho or Galba coin would be more expensive. I don't specialize in this type of coinage, but there are reverse designs for certain emperors that command premium prices. As for the eastern tetradrachms, that's more complex, since there are many mints that produced these coins, many very rare. Antioch seems to be generally the most available. Again, if you are focusing on the emperors, you might look at coins from this mint first, perhaps Tyre as well. As with Alexandria, the coins generally became more debased moving from the first century AD into the second and beyond.
I'll just add that an Otho tetradrachm from Alexandria or elsewhere will cost you a lot less than an Otho denarius -- but the portrait won't look anything like the image of Otho that you have in mind from Imperial coinage. You won't find an Alexandrian tetradrachm or any other coin minted by Caligula: he issued no coins there.
I just looked at Otho tets, and sure enough they simply resemble Vespasian's bust, or is it the other way around?
Alexandrian tets are pretty easy to come by after they stopped being largely silver and went to the potin standard. I don't know if its necessarily easier to do the full set, but I suspect it would be somewhat cheaper than assembling a full imperial set.
For Alexandria, Augustus does not have tetradrachms although there are other denominations-- almost always very worn yet rather expensive. The later Alexandrian tets are inexpensive. Some emperors will be hard to find and probably very expensive: Pertinax, Septimius Severus, Caracalla, Geta, for example.
I love Roman Alexandrian tets and drachmae and other coins, but not really so much for the Emperor portraits -- it's for the interesting reverses, of old Egyptian deities, and zodiac signs, and pharaohs, and snakes and elephants and crocodiles and mummies and Canopus jars, and Tyche reclining on a couch looking like she's steering it down the Nile with her rudder, and Isis nursing the infant Horus, and other things that one can rarely if ever find on Imperial or other Provincial issues. A lot of the later ones, that just have eagle after eagle on the reverse, are of no interest to me.
I'm not sure I see the resemblance to Vespasian. They look kind of like a generic emperor to me, suggesting that the provincial mints really had no idea at all what Otho looked like.
This thread has been quite a flop. I expected people to post the Nero coins that used reverses of earlier emperors as space fillers but there still is no Caligula. If you read up on what was going on in Alexandria during Caligula's reign, you might understand why his coins are not to be found. I do not have an Augustus but here is Nero with reverse honoring Tiberius. There are especially interesting Alexandrians of Claudius. You omitted Pescennius but at least his coins exist. There are no Didius Julianus. I do not have an Alexandrian Otho but preferred what I considered an acceptable Antioch considering what the denarius of the same price would look like. The Rome mint coins really emphasize his ridiculous wig which explains part of why they are so popular.
