Eric:
Milne regarded the appearance of a
star or crescent (or a small
snake as a sign of an
aegis) as either a mark of a new series or a
shop mark, which is what is used in the later operation of the
mint. It might also be a means to identify the die carver. During the
Diocletian period, coins with a
star were carved by the same die carver but were often struck in different officinas-- the 3rd or 4th
officina.
Early
Hadrian tetradrachms were issued in series, that is, one series of multiple
reverse types, followed by another similar series later in the same year-- likely multiple series each year. In the
catalogue sequence in which
Milne identifies the
reverse types it appears he did not consider them to be done in parallel series. So
Milne is not certain if the stars, crescents, etc. are
mint marks, which would be needed for parallel series to note officinas.
The bronze series do not, I believe, have stars, crescents or
aegis.
The
style of Hadrian's
portrait changed in year 9 to a more realistic one, to a backview bust-- likely why the pattern ended after year 8.
Iwaniw
