There are some clues as to date. I suspect it's later than 17th century and unlikely to be mid 16th century. But your guess is as good as mine.
Clues:
Iggy has a halo on the medallion. He wasn't a saint until 1622 so it has to be later than that date and probably several years to make a medallion and transport it to the new world, overland by foot to southern AZ. It's possible but unlikely to fit conquistador era.
Iggy is portrayed facing right and wearing a full beard. In general saints are most often depicted face left by custom at the time, face right was generally reserved for royalty. Most of the early depictions of Iggy have no or minimal facial hair. These aren't hard and fast rules, there are certainly exceptions, but seeing both in the same piece causes me to question an early date.
That being said there are probably literally millions of Loyola medallions sold since 1622 so unless you can find a complete authenticated example it's going to be difficult to pin down a date without investigating the metallurgy.
