Quote Originally Posted by The Persian Cataphract
You mean in the "Seleucid Armies"? The fillet, though a mainly "cosmetical" head-piece, had a function which is possible to date to Achaemenid times where the Medean fashion was the norm. Plutarch describes Surena as a man dressed in Medean fashions, as well as having "parted his hair in the Medean style". I think you are confusing the fillet with the diadem depicted in mints and in some very rare graphic depictions, which were merely symbolic and often depicting coronations and/or investitures. The diadem was often little more than a piece of fabric, only made a little more elaborate during Sassanian times, however by the time of Mithradates II The Great, a new type of regal headgear was introduced with strong Persian influence, and this was the tiara. The mints of Mithradates II The Great were so popular that they continued to even be copied by the Sassanians during the reign of Ardashir I. Otherwise the fillet has a longer story within Iran proper, in which one of key elements in ancient Iranian cosmetics was the grooming of hair, and additionally even facial hair. Looking at the statue of Surena reveals a very distinct hair-style, and looking at how the chin-strap is depicted in certain regalia of the Sassanians, I'd say that there is more to the issue.
I don't see how you could effectively distinguish between the fillet and the diadem in many cases since they looked very similar.

"Saka" is very ambiguous and remains so as the Greeks made no distinguishment between Scythians (Besides the Massagetae and various other obscure tribes) and the Achaemenids were no different in their collective designation. The Parthians themselves were of Scythian origins (Pârnî means "exiled") and the Dahae too were in all possible aspects Scythian. The Parthians by this time fought a multitude of enemies, including the Dahae, and this could also imply that at periods there was internal strife as well. This piece was found in Mithradatkart, in the very heart of the Parthian homelands, in a time where the Parthians were not so aggressive in their expansion.
If this does date to the 2nd C. BC, then it would have been made in a time of considerable expansion within the Parthian empire. And in this fresco, there is apparently a difference in the colours and appearance of both horsemen, implying that one is a different group than the other (though, of course, different rebel groups would have been differentiated as well). Of course, since the dating of this piece is uncertain, "Saka" is just a guess; we will never be able to specifically identify this fellow or his companions.

There is a Soghdian Parthian belt plaque showing heavily armoured cavalrymen and infantrymen in the more classical "Eatern Scythian" style, including wide chaps and oven-man coats of lamellar.
Do you mean te Orlat bone plaque? The general consensus is that it dates to the 2nd-4th C. AD. Or are you referring to something else? Could you post a picture?