The coin evidence dates the sanctuary to between about 80 and 171 AD, during the period of the Roman cohort fort in Kumpfmühl and the associated Danube settlement, before the establishment of the legionary camp at Regensburg.

This is interesting because it shows how widespread the “mystery cults” (like Mithraism) were back then.

Originally the Romans built a small fort in the place, near the Celtic settlement of Radasbona. But then by 171 Marcus Aurelius had it rebuilt to host the Italic Third Legion. And given legions back then had 5200 soldiers, this means the fort was considerably smaller than the necessary to hold 5k people; if it was just a bit smaller, they’d extend, not rebuild it.

For reference: in the 1st century it’s believed the city of Rome had ~1M inhabitants, and Alexandria had ~500k. The empire as a whole had, like, 60M? 75M? inhabitants. So even for the standards of back then, this sanctuary was found in the middle of nowhere, and yet there was social pressure to build a shrine for Mithras there.

the sanctuary provides valuable new evidence for the rituals and material culture of the enigmatic Mithras cult across the Roman world.

That’s important because we know practically nothing about the cult. The initiates swore an oath of secrecy, so written info from those times is rather scarce.