French Hallmarks in Turkish Pendant

[wiggy131]

Hello, Not sure, but think this a Turkish design set with blue stones, cant see any air bubbles through the blue stones.
Any thoughts on the stone, I thought blue topaz?
It has a French Silver hallmark with a crab and then a makers stamp. Looks like RK with an N in a circle at the middle.
Does anyone recognize the maker?
Thanks again
Vickie

[bijoux.expert]

Not Turkish, Algerian, with French crab hallmark. Perhaps the assay office of the t_own of Bone, but not certain.