Sorry…keep trying! Hint - if the mantle over his head throws you off, imagine him without it, and then you might recognize him from another statue, which is one of the most famous of all Roman statues.

Yes!  Caesar Augustus it is.  The portrait of him with the mantle over his head is where he is depicted as “pontifex maximus” (chief priest).  He is recognizable for his idealized face and his distinctive hairstyle, which basically forms comma-like curls on his forehead.  There would have been some official portrait of him that was copied and turned into other portraits.  He was depicted as 25-year old (give or take a few years) in his portraits, even later on in life.  Here is the more famous Augustus of Primaporta. Statue-Augustus [CC-BY-SA-2.5 (www.creativecommons.org/licenses/by-sa/2.5), GFDL (www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (www.creativecommons.org/licenses/by-sa/3.0/)], by Own workOriginal by Andreas Wahra, new version by Till Niermann, from Wikimedia Commons