What era and possible value of a ring

I have a ring that was my great grandmothers wedding ring from 1899. It has crossed rifles stamped inside the band as the jewelers mark and it is a dark gold probably mixed with copper or another metal.

There are 3 blue stones (i was told blue diamonds) that are in the center of ring in a row that run vertical on the finger. I am trying to find out a aprox value. I have had several people notice it with very wide eyes when I have worn it and they approached me to sell it to them but stating they only wanted the gold !

I am now afraid to leave with it anyone to have it appraised ! Any suggestions ?