Same Mintmark, Different Attribution

My track record has been bad lately as far as attribing goes. But I make them to be Siscia 369. There is a slight difference in the style of the horsemans helmet. Could that be why you get two different numbers?

Wow! That's much different from my attributions. I think the "hat" is the same for both, so I didn't make a distinction for that. The difference I see is the circle (globe) at the left foot on the Roman soldier in the second coin. RIC 369 has an M in the left field where neither of these do. I also think the mintmark is A or Delta SIS zigzag, not B.

Is the lower coin ever so slightly larger diameter than the upper? It strikes me as an RIC 352 page 375. RIC does not mention the omission of the shield on 361-367 but my example of 361 lacks a shield but has a lump under the foot as if the soldier were standing on something not clearly defined. The difference between these numbers is mostly whether they were issued while Constantius Gallus lived or after he was replaced by Julian. RIC gives them the same weight but a larger diameter expected of the Gallus period issues. There are coins that are hard to separate with certainty but if you had a hundred mixed coins of the three rulers it might be more obvious which Constantius II possibly went with which Caesar based on 'fabric'. People who write RIC have access to such groups of coins but we do not.

Any time you get a question on horsemen, I suggest looking over Dane Kurth's coins and see if you see a clue. After you look and fail, I see nothing wrong with sending her an email with a specific question. Looking at her coins, the one with a clear, round shield is listed as a 361 (the opposite of my guess). If the question were mine, I'd ask. She is usually quite nice and helpful. Who knows, you might get another coin on Wildwinds.
http://www.catbikes.ch/helvetica/ft-siscia.htm

I heard back from Dane and she doesn't think there is anything about either coin to distinguish either:

"Well, when you consider the number of these Fel Temps
that were issued, especially from Siscia, they must
have gone through a heck of a lot of dies.
I think the soldiers foot is on a small shield but it
is practically invisible because of the O of REPARATIO.
Maybe he made the figure of the soldier nice and large
not realising that the legend had to be added and that
he would have to add a very small shield.
These saggy wreath ties and weird long face, as well as
the often huge point on the Phrygian helmet, are so
typical of Siscia, so there is no question of this
being a barb or something. I wonder how many dies they went through ? I have over 1,700 Fel Temps and not a single die-match from any mint."

Now I'm on a mission to see if I can find any die matches. It may be impossible, but it's something to watch for.

I am amazed that Dane has no die matches but I suppose the huge number of coins makes this believable. For comparison my collection of Eastern mint Septimius Severus denarii has something approaching a third of the coins involved in a die match. There are coins known from only one die set so every specimen is a die match. This makes zero out of 1700 quite a statistic.