Mizpah Ring

I have a custom made gold ring with the makers mark L&J. It also has other marks...one looks like a crown perhaps, and the other I can't make out. The ring belonged to my Grandmother who lived in Great Britain.

It has 25 diamonds (not chips) that spell Mizpah. Mizpah: the Lord watch between me and thee, when we are absent one from another. It was made for and given to her prior to my Mother's birth in 1911. Probably in the late 1800's.

My Grandmother was Catholic and the man that gave it to her was Jewish. The story goes...he admired her, but the difference in their religions made them being a couple impossible. He gave her the ring and left England.

Can you help with any information? How do I find someone to appraise it properly? Thank you for any help you can offer.
Alexandra