P M TR P COS P P

Laureate, draped and cuirassed bust of Gordian I Africanus to the right, seen from three quarters back.

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

Photo of a coin sold the 17/09/2014 by Classical Numismatic Group, Auction 97, lot 688, link to the sale: https://www.acsearch.info/search.html?id=2122867, link to their website: https://www.cngcoins.com/.

This obverse legend IMP CAES M ANT GORDIA AFR AVG was first referenced by Gorny & Mösch. I shown the coin to Mr Curtis Clay which links it to a denarius of the same legend (see Gordian II AYC #2, RIC - ). I quote Mr Curtis Clay during our discussion: ''the variant obv. legend on the Gorny & Mosch sestertius must be original, because the same legend also occurs on a very convincing denarius not sestertius, of Gordian II not Gordian I, with different rev.type PROVIDENTIA AVGG, in the collection of... 
In my opinion our conclusion can only be, that the first obv. legend of Gordian I and II, used very briefly on all three denominations at the mint of Rome, was IMP CAES M ANT GORDIA AFR AVG. From this issue only the Genius of the Senate sestertius of Gordian I and the Providentia denarius of Gordian II are so far known, but other sestertius and denarius types, and possibly even aureus types, may be expected for both emperors. Very soon, however, the mint switched to the two obv. legends which until recently were the only ones known, IMP CAES M ANT GORDIANVS AFR AVG on aurei and sestertii of both emperors, and the same legend without CAES on the denarii of both emperors.''.

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. 

Gordian I and II share the same obverse legend, the bust of Gordian II is distinguished by absence of hairs in front of his laurel wreath.