https://en.numista.com/catalogue/pieces10302.html
Maybe - as it should be 17.5mm but yours has edges clipped so could be correct.
(France - Feudal) Comtat Venaissin
Patard d' Avignon - Urban VIII
Obverse: Crossed keys
Lettering: VRBANVS VIII PONT MAX
[URBANUS VIII PONTIFEX MAXIMUS] = Urban the Eighth, the Greatest Priest
Reverse: Cross in quadrilobe
Lettering: S PETRVS ET PAVLVS AVEN
[SANCTUS PETRUS ET PAULUS AVENIONEM] = Saint Peter and Paul, Avignon
So then ??LVSAVINSI?? is ...LVS AVEN / S P..... .. ... with ETRVS ET PAV missing/clipped.

[known in yellow, missing in green]
https://en.wikipedia.org/wiki/Pope_Urban_VIII
https://en.wikipedia.org/wiki/Pontifex_maximus
However, if not Urban VIII then maybe Paul V instead.