Antique Art Deco Emerald Ring Help!!!

[tessaroni3]

Hi there! My name is Tess, and I have decided to buy myself my first piece of "real" jewelry!!!! YAY!!! I want it to include emerald, my birthstone, and I want it to be antique, preferably art deco. I have done a ton of looking at rings, but I don't know the first thing about them or the lingo. I have fallen in love with the way the look of old camphor glass rings, with the little diamond set in the center. I have been looking for a variation of this with emerald, but I don't think it exists! What is it called when the diamond is placed in the center? How do I even search this? What would it take/cost to get one of these little diamonds replaced with emerald? Any help is welcome, even if you want to make fun of how little I know about this stuff. Thank you for your time!!! I attached some pictures for examples of what I'm looking at.