So I've had this coin for a while and formerly had it catalogued as a Constantine I coin, making the fairly common mistake of believing that the MAX in the legend CONSTANTINVS MAX AVG meant that it was Big Daddy's coin. I've since learned that Constantine II also used this legend, and by comparison to coins at Wildwinds, I have conjectured that this is Siscia RIC VIII 89, with ASIS crescent as the mintmark. It's a very common coin, but the clear Chi-Rho at the top of the reverse standard makes it a little more interesting than the typical Gloria Exercitus. My question for the LRB experts out there: Is there any dispositive, easy giveaway that marks this coin as Constantine II and not Constantine I, or does this distinction have to be made on style alone? Using Guido Bruck, it seems that Constantine I struck Chi-Rho Gloria Exercitus coins only at Arles. So a Chi-Rho from any other mint must be from Constantine II, is that correct?
It turns out to be provable that your coin was minted after Constantine I's death. @Valentinian talks about this very question (only with respect to the chi-rho coins, but the lesson might be extendable) on his page here. To quote (boldface added): "None of the Siscia coins are of Constantine I -- even the coins like this one with his portrait and legend are really of Constantine II who assumed the titles of Constantine. This is easy to prove because there are no coins of Siscia with chi-rho minted for the Caesars -- all chi-rho coins of this type for Constantius II (next) and Constans (second next) have obverse legend with AVG. This contrasts with Type 1.12 of Constantina (= Arles) which appears for Constantine as Augustus and all the Caesars and Delmatius." So the giveaway is that it's Siscia. Here's my example of the earlier Esty Type 1.12 of Arles (in this case, Constantius II as Caesar):
That's a cool little chi-rho above the banner! I've got a Constantine II MAX, here is my last uncleaned lot coin. Came out pretty nice! Constantine II, 337-348 AD O: CONSTANTI-NVS MAX AVG, R: GLOR-IA EXERC-ITVS, dot ASIS star in ex. Siscia mint, RIC VIII Siscia 79, 17 mm, 2.0 g