Diodotus Tryphon was a Seleucid usurper who managed to hang on to his throne for a good four years. There is a coin type unique to his rule, and this is the first example I've handled, so I'd like to share it. The reverse depicts the national helmet of Greco-Macedonian soldiery, with cheek flaps, adorned with an ibex horn. The design also comes in tetradrachm versions. I'm not sure the ibex horn would have been of much use in battle, so perhaps what we're seeing here is a ceremonial helmet - perhaps only for those of high rank? Tryphon also took the title AYTOKPATOP (the Greek equivalent of the Latin Imperator), which is the only time the word occurs on Seleucid issues.
Mine is similar with a smaller helmet making room for a larger finial. I'd need to research it more but equating AYTOKPATOP with IMPERATOR does not strike me. Auto means self and krator means ruler so autokrator would be the term for a top level, answers to no one, ruler - a self made man responsible for his own position. This would be most appropriate for a usurper who defeated a hereditary king. Imperator was awarded to generals who achieved success but who still answered to the state or emperor (then called Augustus). Yes, we get the word emperor from imperator but the original meaning of that word was closer to generalissimo. Should we note that portraits of this ruler show hair uncombed or, perhaps, 'helmet head'.
Good points. Yes, helmet head! It makes perfect sense. I'm quoting Varbanov in the translation of AYTOKPATOP to Imperator, but your analysis makes much more sense. Leave it be as a Greek word and never mind the translation.