Antique 2 sided Pendant

This pendant is 2.75" x 1.75" it is two sided.  On one side is a portrait of a woman sitting, she is wearing a puufy sleeved black dress and a very ornate lace 'bonnet' and neck covering.  She is holding a book.  The artwork when looked at under magnification is amazing in detail.  On the other side of the pendant it is predominently gold with a large oval stone in the center.  Silver rope details accent the perimeter of the pendant as well as around the stone. 

I believe that this pendant would have been worn by a man with the portrait facing his heart.  This is a very old piece that has been passed down from generation to generation.  I would love to know the age of the piece and any and all information you can provide me with... I have done extensive research and cannot find anything remotely similar, so I have no idea of the value either...

Fair