R.C., This is an interesting thread with great examples posted by CT members . For comparison below is my favorite Greek coin with Artemis sporting a stephane. IONIA, Magnesia ad Maeandrum, circa 155-145 BC. Obverse Artemis, reverse Apollo. AR Tetradrachm: 31 mm, 16,89 gm, 12 h.
A most informative write-up, once again, RC. Here is the same reverse type of Faustina II on a pair of sestertii, one without and one with the stephane, resulting in sequential RIC numbers, but a "var." for Sear, if I got my attributions right: Faustina II the Younger Æ Sestertius Rome Mint (161-175 A.D.) FAVSTINA AVGVSTA, bare-headed & draped bust right / TEMPOR FELIC S-C, Faustina standing, holding two infants, four children at feet. RIC 1673; Sear 5284 (var) (21.56 grams / 30 mm) Faustina II the Younger Æ Sestertius Rome Mint (161-175 A.D.) FAVSTINA AVGVSTA, draped bust right with stephane / TEMPOR FELIC S-C, Faustina standing, holding two infants, four children at feet. RIC 1674; Sear 5284. (22.81 grams / 32 mm)
Galeria Valeria 25 mm. 6.21 grams VENERI VICTRICI SMSD RIC VI Serdica 41 "late 307-8" I don't think coins of Helena show a stephane like in the OP. This AE4 shows some sort of hair ornament, but it is not the same. Fausta was not "Augusta" and her AE coins do not show a stephane. Aelia Flaccilla, wife of Theodosius, and Eudoxia, wife of Arcadius, held the title Augusta but their AE coins do not have a stephane. So, maybe Galeria Valeria was the last. Can anyone show a later stephane on Roman coins?
Fausta example coin from Killingholme hoard: RIC VII, London, Fausta, No. 300k Killingholme Hoard (Trier Mint) - 324 to 325 O: Fausta bust right - FLAV MAX FAVSTA AVG R: Fausta holding two infant sons - SALVS REIPVBLICAE There were several very fine coins in that group that I purchased - attached here is a Fausta reduced follis. I do not know why the patination differs between obverse and reverse - maybe as a result of contact with different substrates over a long period of time?
I also have a coin with different obverse and reverse patination, and was told that maybe the coin was more exposed to light on one side than on the other. That I should turn it, which I haven't done. Don't know if this could also be a reason for the difference.
One question I haven't really seen discussed in this thread: at what point does one consider a diadem to be a stephane? I think that's an especially relevant question in looking at Roman Republican examples, like the ones that @Orielensis posted. Here are my own denarii of Naevius Balbus and Caecilius Metellus, showing Venus (or Juno) and Pietas, respectively: In my mind, a stephane is shaped more like the prow of a ship than an "ordinary" diadem, so I might be more likely to say that Pietas is wearing a stephane on the Caecilius Metellus, than that Venus/Juno is wearing one on the Naevius Balbus. I think both can have jewels on them, so that shouldn't be the basis for a distinction. What criteria do others use for distinguishing between the two?
Semilibral anomalous series. AE Triens, c. 217-215 BC. Obv. Diademed female head right; behind, four pellets. Rev. Hercules fighting centaur, holding his hair in left hand and club in right; before, four pellets; in exergue, ROMA. Cr. 39/1. but to me it is more a stephane