Help with identification of mint mark

Can anybody help with the identification of the mint on this follis of Constantius II. The coin has a small flan, but the mint mark is clearly legible as RBT.

Is this a Trier or Rome mintmark?

 

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it's from Rome

 

That was fast .... many thanks! (The expertise on this forum is quite remarkable)

Best
Dirk

 

the RB in the mintmark likely/maybe stands for Roma Beata (Blessed Rome) and the T is the workshop.

 

Interesting.
I used the sources below but could not find it:

https://www.forumancientcoins.com/numiswiki/view.asp?key=mint marks

https://finds.org.uk/romancoins/articles/page/slug/fourth-century-mints


But now were I know the mint, I found many examples here:
http://www.nummus-bible-database.co...26&nombreResultats=50&btRechercher=Rechercher

 

I have two more mints of this type: Antioch and Alexandria. I kind of like the Empire's small change:

 

Just saw that I also have Arles and Aquilea (I always wondered what the symbol between the two soldiers on the Aquilea issue is meant to be - a cross or an Egyptian ankh sign?):

 

Trier is usually TR-, with the T in front. If T is in the end, it's more likely the officia number.

Here's a (potential) imitation, but has the Trier mintmark: