Beach Find Ring

I found this ring on a beach recently. It has forget me not flower designs around it, and is of a basket construction so not heavy. A jeweler told me it is 8 or 9 ct. gold, and has a real albeit tiny black diamond in the center. An antique dealer told me it is a remembrance ring from some time in the early to mid-1800s. It would have been given to a daughter by her parents when she left home.

Does this sound correct, and do you have any information on this type of ring.