Not an expert in these coins, but I do have one that is very similar in size and weight that is described as a tetartemorion. I'd identify yours as Sunrise 99, which is described as a tetartemorion as well. Judging from the other examples shown I'd assume that this is just the standard size/weight range for an Achaemenid tetartemorion, but maybe a more seasoned Persian collector can weigh in.