Personally, I wouldn't get my hopes up too high just yet. being set in silver is a sign it's likely simulated emerald (glass). My grandmother had many such pieces of jewelry which were popular around the art deco period. I would think that a stone of that size and value would be set in gold instead. Not sayng it isn't possible though, so to be sure you would need to get it checked out.
If it's real, I looked up some prices of loose emeralds. The good quality dark green (as this one appears to be) 1.5 Ct. go for around $4000 to $8000. Guestimating by comparing to the paperclip, it would measure about 7mmX9mm, which puts it around 2.5 Ct. from examples on the web site I checked. Stones of that size I looked at published prices from between $2000 and $27,500!
So keep us posted on what you find out! Good luck, and I really hope that it's genuine!