P M TR P COS II P P

Laureate, draped and cuirassed? bust of Pupienus right, seen from three quarters back. 

The genius of the senate standing left, holding a branch with the right hand and a short scepter with the left hand.

One coin sold the 20/05/2013 by Bertolami Fine Arts, Auction 7, lot 746, link to the sale: https://www.acsearch.info/search.html?id=1592923.

The AYC #28, RIC 15 is the only coin whose cuirass is clearly visible. On all the other coins that I could observe, the cuirass seems absent. The shoulder is smooth and the lower part does not have a sawtooth shape as is the case when a cuirass is present. However, I chose not to classify a only draped bust for this type. Indeed, I observe that in general the cuirass on the busts of all the coinage of Pupienus is very little visible (see comment below). So I'm waiting to be able to see a coin where the shoulder is undoubtedly smooth. For the moment, taking into account my remarks on the visibility of cuirass on the coinage and adding that the shoulder is one of the most prominent elements and therefore highly exposed to wear, it seems to me too early to conclude that a only draped bust exists. We must remain attentive to this subject because I have already demonstrated here: https://www.all-your-coins.com/en/blog/antique/romaines/les-bustes-seulement-drapes-de-balbin-a -gordien-iii, that a variant of only draped bust exists for Gordian I.

I observe that on most of Pupienus' coins the cuirass is almost invisible and the shoulder appears smooth. Although I have listed a variant with a non-cuirassed bust for other emperors from the same period, this bust of Pupienus seems to be cuirassed. We see streaks indicating a cuirass in the lower shoulder or at least an irregular lower shoulder showing a desire to display a cuirass. Here is an example:

 On this photo the streaks are visible at the bottom of the shoulder. 

However, we cannot exclude that only draped busts exist. So far, I haven't noticed an example where the shoulder is undoubtedly smooth. 

A coin with type P M TR P COS II P P (no way to know the legend break) has been overstruck with a LIBERALITAS AVGVSTORVM reverse. See photo on the comments of AYC #25, RIC 14.

I noted "genius of the senate" on the reverse unlike RIC 4B which notes "the emperor standing on the left ...". Indeed, this character always appears at the same age and bearded whether it is for emperors bearded or not, young or old.