When it comes to fourrees, pretty much anything goes. I remain of the opinion that some, at least, makers wanted to be able to tell their work from the good stuff so they could distance themselves from the bad coins. This one is FORTVNA PR which is a normal Nerva type and the obverse legend is Nerva. To me, the portrait was done by someone who had seen Trajan or Domitian but not Nerva. I like fourrees that have unofficial style which one could make a case for being better executed than the official dies.
Cool coins, gang (some of them => amazing) ... Ummm, and amazingly I haven't posted my only Nerva yet!!? => oh well, here it comes ...
We can never know for sure but I like to think that after Nerva died, one of his dies was snuck out of the mint. It took a while to pair it up with a reverse at which time only Trajan dies were available. The forger possibly didn't realise the COS IIII/II combination, or didn't care. The engravers needed to be literate, not so much the forgers.