Voulan said:
Many of the Elite Roman families wore rings with the family insignia to demonstrate their power and status. This could easily be a symbol of a family that ran a successful shipping company (many Elite families has their own ships and ports) before any of those symbols meant anything to do with Christianity.
Yeah, this is what I first thought as well. As a matter of fact, in my Early Christianity classes (I'm an archaeologist), our professor said that even though the fish is a symbol for Christianity, it is not always used in that context, especially prior to the 4th century. She explained that finding a fish as a symbol somewhere is not a certain indication that the object or the place in question is related to Christianity per se. It
could be, but just spotting a fish and declaring the thing Christian is not good. There needs to be more evidence for this, because a fish is a very common symbol that pops up in a lot of places and has been popping up for a long time before and after Christianity became a thing.
But it would be very interesting if it really was an early Christian ring. I hope they manage to prove that somehow, but something so small and portable could have ended up there in a lot of ways (just like you said, someone could have been visiting them and lost the ring) and could have a lot of meanings.
An even more interesting turn of events would be if the ring indeed ends up being the Ring of Power. One can dream.