Vintage/Antique Locket

Hello!

First off, I believe you are wrong about the engraving. I believe it is a dagger through a heart, with flowers and leaves on either side, and that the "diamond" in the center is a cross with either a thorned crown, or the wound left by the spear as Jesus was on the cross. Classic christian symbology.  I could be wrong though, hard to tell from the photos.  

I couldn't find your exact pendant anywhere, but gold plated jewelry usually isn't very valuable.  

Hope this helps.