Confirmation Request for 3rd century Roman Coin

Good evening, 

I’d appreciate confirmation of this attribution.

Coin: Probus (AD 276–282), antoninianus (silvered)

Obv: IMP C M AVR PROBVS AVG, radiate cuirassed bust right

Rev: CLEMENTIA AVG, Probus and Clementia standing facing, holding wreath

Marks: P in field; B above XXI in exergue

Measurements: 21.97 mm, 4.49 g, 1.82 mm thick

Proposed mint: Rome, officina B

Reference: RIC V.2 Probus 171

Does this look correct, and is the mint/RIC number accurate based on the P + B/XXI mark combination?

Thank you for your time.

This got more tricky than anticipated.

First of all, the obverse lettering is correct, but the reverse lettering is CLEMENTIA TEMP.

With B in field and XXI in exergue.

Now comes the tricky part. There are two RIC entries with that combination: 

- RIC V.2 Probus 644 from Sicia - https://numismatics.org/ocre/id/ric.5.pro.644 - N#293000  and N#293645  (I think we have a duplicate entry here)

-RIC V.2 Probus 921 from Antioch - https://numismatics.org/ocre/id/ric.5.pro.921 - N#101254 

Since they are too similar and have the same combination of letterings of yours, I think we'll need someone more expert than me to help differentiating these two and determining which of them is yours.

This is quite frustrating. I've checked the RIC cataloge directly and it has the same data as the OCRE an Numista, so it's not just someone made a mistake copying the data from it.
 

The lettering is the same for both coins as well as the B/XXI mintmark.

RIC V. 644:


versus RIC V. 921:



There are just two small differences betveen them. The 644 can have a cuirassed bust, while the othe can't. And also on the 644 there supposed to be an eagle on the top of the scepter of the emperor. I'm not sure if this is a genuine difference, or the description is just shorter on 921 and that's why it doesn't mention any eagles.

I've checked the images of both coins on OCRE but I can't really see a difference neither on the bust of the emperor (cuirassed or not) or on the top of the spectre.

Holy doppelganger Batman.

What do we do now?

I don't know. We can't really just merge the two pages. First of all, which page should stay and which one should go? And eventually someone would recognise that gap in the RIC numbering and re-create the deleted page anyway.
Maybe just put a cross-reference on both pages? But that's not a real solution either, as someone sooner or later ask if their coin is from Siscia on Antiochia after all.
Maybe there is some difference between them that is not captured in RIC? The weight/size are quite uniform, but maybe the composition is not?

The only merge we could make is about the two pages for the RIC 644.

I got an idea: How about calling in @cro321 ? He's an expert on Siscia coins, he may help on this case.