Identify Ring #4

I have to admit that when I am metal detecting and see a ring like this pop out of the ground, I get a little excited.  It was pretty dirty, but it had what looked like some big diamonds.  Finding a ring with some real diamonds is probably my only real chance to recoupe the money invested in this hobby.

One of the first things I noticed about this ring is that it appeared to be flaking some sort of plating.  That pretty much convinced me that it was a fake, but as I got it home and cleaned it up and put it under the microscope I have to re-question my first assumption: Is it real?

There were 2 hallmarks stamped in the ring: 925, and FAS.  925 usually means sterling silver, but I had never seen the FAS hallmark before.  Google suggested that it meant "fused alloy silver", which would make sense with the 925 (92.5% pure silver).

What do you think?  Is it real?