Mint error, strike issue, or just bad eyesight?

[Restitutor]

So I'm currently engaging in a rather large project, to re-photograph all my coins and ensure all the references etc. are accurate. As I got to this coin, I'm left scratching my head. Here's mine:

Underneath Liberalitas my eyes clearly see LIB III. So clearly I almost didn't even think about it when looking at the reference. However, I went to WildWinds and for this exact type, it says it should be LIB IIII. Here's the photo on the site:

 

LIB IIII is clear as day! From here I just checked elsewhere on WildWinds to see if there's a LIB III. No dice. There's only one other style of this coin on WildWinds and it has the LIB IIII to the left and right of Liberalitas, respectively (shown below).

Then I went back to staring at my coin to see if there's any way I missed another I. Given how the III on my coin curves up and to the right, I don't see how it could be a strike issue as even in the WildWinds example the IIII curve up and to the right. Maybe my eyes are failing me though. Or maybe the WildWinds archives are missing this example?

The longer I stare at mine the more convinced I am that this reverse die was incorrectly made with only "III' and not "IIII".

What do y'all think?

[expat]

The 4th I could possibly be a striking anomaly, there appears to be a feint partial impression in the correct place. The first example on the link shows a similar weakness in that general area.

https://numismatics.org/ocre/id/ric.3.ant.155_denarius?lang=en

[Spaniard]

@Restitutor..Nice looking coin! And an interesting project, something I need to start aswell..

I'm seeing the first I after the B, or at least a darkened space where it should be? I agree with @expat something amiss with the die maybe blockage or foreign body stuck to die when struck?

I have the type 1...

Antoninus Pius (AD 138-161) AR denarius, struck AD 145-161. Rome mint.
Ob..ANTONINVS AVG PIVS PP,(Antoninus Augustus Pius Father of the people) laureate head right
Rev..TR POT COS IIII,(Tribune of the people 4 times Consul) Liberalitas standing left, holding abacus and cornucopiae, LIB IIII across the fields.
RIC #155 type 1
This coin commemorates Pius' fourth largesse distributed to celebrate the marriage of his daughter Faustina II and Marcus Aurelius Caesar in spring 145 AD.

[Restitutor]

Thank you both! That seems a far more reasonable explanation than me having seemingly the only version of this coin in existing with only 3 ‘I’s. Although a tad less exciting 😆 time to update my records!