Heirloom.

Okay vintage lovers!  I've been blessed to be handed down an heirloom from my aunt, my grandmother (and maybe her mother?).  I've been doubly blessed to realize that it fits my big, fat, prego fingers, so I no longer have to look illegitimate! (This is rather important to me.)  So here's my query: What era does this ring date back to? And, can you tell me anything about it?