Pretty sure the host coin is a Sasanian-imitative, maybe one of the Hunnic tribes. Agreed that the countermark head does resemble a Parthian, probably coincidental as the Parthians were long gone by this time. Interesting, worth further research.
My understanding is something like this. After the defeat of the Hephthalites in 560 by the Sasanians and Western Turks in coalition, Tokharistan (Bactria) splintered into a number of principalities, some directly ruled by the Sasanians, some directly by the Turks, others by Hephthalite or local dynasties. Zeno attributes this countermarked type to 7th century Kobadien/ Kobadian/ Cobadian (Tajikistan). The countermarks are likely a bit later than the host Peroz imitation itself. https://www.zeno.ru/showphoto.php?photo=37757 https://www.zeno.ru/showphoto.php?photo=156002
