I think the term Sarmatians is kind of analogous to the term Goths. Both names were (sometimes more and sometimes less) used as umbrella names for different tribes or groups. The Romans counted Tervingi, Greuthungi, Vesi and Ostrogothae as Goths (sometimes also Gepidae were called Goths), while Alani, Jazygi and possibly Taifali were deemed to be Sarmatians.
Of course there is no material evidence for these hypotheses. The estates granted to Barbarian warlords were just a source of income, it does not mean the Sarmatians, the Alamans (cf. all these places in France called "Allemagne"), the Alans ("Alaigne"?) had to settle there and forget some typical objects of their home country. Toponymy in France is most often reminiscent of the owner of a place at some stage of its history, or of the saint whose relics were kept in the local parochial church. Savignac, Savigny is most probably "Sabinus' estate", "Pont l'Évêque" a bridge that belonged to the diocese bishop. "Chaussée de César" means "imperial road". What else could "Sermaize" mean? May it come from "sarmentum", "sarment" (a dry wooden branch?). The owner's name hypothesis seems more likely, "Sarmatia": the estate belonging to Sarmatians. We do not know where those Sarmatians actually lived, and in which conditions (a camp? a village of Gallic houses?), but the hypothesis is that the estate income was for local Sarmatians. It is a mere hypothesis, of course !
Something different ( i don't own an official type ) Unofficial / imitation, with a retrograde Reverse, Trier
That's awesome, now you need to get an official Trier example. I don't have an unofficial SARMATIA but I have an unofficial issue of Constantine I paired with the ALAMANNIA DEVICTA type; which was never offcially struck for him. Constantine I Circa A.D. 324- 325 18mm 2.1gm CONSTAN- TINVS AVG; laureate head right. ALMANNI-A DEVICT; Victory standing right, on bound captive with head turned to the left, holding laurel branch and trophy. In ex. SIRM
This is correct. Here is a wikipedia article (I know it isn't the most reliable source) about a semi-nomadic Sarmatic branch, the Iazyges, part of the Alanic group https://en.wikipedia.org/wiki/Iazyges Their name survives today in some geographic names, such as Jászság region in Hungary and Iasi, the city I live in.