This coin is 18-17 mm and 1.83 grams. At first you will note the radiate bust left. It has a legend break
CONSTANT-INVS IVN xx [x for uncertain]
and a bust possibly seen from somewhat behind.
The reverse looks much like a standard Lyon issue with
C R as controls marks above PLC in exergue
The reverse legend is shorter than normal
BEATA TRANQVILLIx
around the usual altar with globe on it and three stars above.
I can't match the radiate crown, the legend break, the final obverse letters, or the reverse legend to the many examples of C R over PLC in RIC VII, pages 130-134.
I suppose it could be an ancient imitation, but, if so, it is a good one. I solicit your thoughts.