Indeed it is, of Maximinus II.
Yes. All coppers in the tetrarchy period are follis except for some scarce half and I believe quarter follis of the pre-reform period. They are pretty scarce, though, so I doubt you will run across one easily. Still, if its Diocletian or Maximian and this size you can always check to make sure its not a prereform half follis.
I was taught starting around the time of Constantine/Constantius II you start classifying the coins as AE1-AE4 based on size, but I see now they call one size at least a centenialis. I just use AE1-4 with 1 the largest, and a 4 being smaller than 15 mm.
The follis name returns starting with Anastasius, who reformed the bronze coinage to make 40 of the tiny little old coins worth one new follis. The follis name continues with byzantine bronzes until scyphate coinage comes into vogue in the 11th century.
Member ANA, ANS, ONS, TCACC, and other random alphabetical concoctions.
Very nice Maximinus/Genius you got there Dutchman.
And I saw heaven opened, and behold a white horse: and He that sat upon him was called Faithful and True, and in righteousness he doth judge and make war.
Follis is really a modern term that means little more than coin but sometimes we see it used as 'bag of coins' indicating it is a larger denomination which might be taken as a unit of five or forty smaller coins (depending on the period). The other abused coin is 'nummus' which also means coin but collectors throw around like they know what it should have meant. The fact is we have a very poor grasp on what the original users of these coins called them. Yours is relatively large and early following the reform of Diocletian. It is common to find these relatively thin coins poorly struck since there was too little metal to fill out both dies. Collectors should pay extra for bodies of Genius with head, feet and all in-between fully formed (this is the 300AD equivalent of full steps nickels). Your coin appears to have been bulk cleaned (maybe tumbled???) rather than from the uncleaned lot ... or am I missing something here? Be very careful reading these coins because a single letter can make all the difference on ID. Maximinus II is correct here (good job, guys). I have a page on that, too.