Here’s a similar Galerius from Alexandria but a bit earlier with him as Caesar. Look at that neck! I also have a matching Diocletian but not yet photographed as it’s a bit ugly. Galerius - Alexandria - RIC VI 48b
Great coins and discussions all! I had always assumed the post-reform radiates to be half-follis coins, although to be equivalent to the pre-reform antoninianus also makes sense - the antoninianus was about the same purity billon as the follis, but not an even fraction of the weight (about 3-4g vs 10-11). Also @Valentinian 's website makes a good point I hadn't though about - since Alexandria was making tetradrachms until 297, they would have had a massive small change shortage, which explains why the radiate was made intermittently until the 3rd Tetrarchy. I do have to disagree about the scarcity though - these radiates show up all the time in large lots.