18th century (?) brass ring with diamond (?) and two others stones

[Richard22]

Found on a 17-18th centuries site, but may be more recent. Have you ever see a ring like this one? The «diamond» glow purple under a UV light. I'm looking for a clue that would help me to date the ring. Thank you!

 

[ColonialDude]

Interesting ring. I agree with the others. It doesn't look 18th century to me. Cool find regardless

 

[Eagleye]

Really nice! Either way it looks pretty dang old