Hi Jay T,
I really appreciate your help here here is a picture of the mark not very well stamped but does resemble a fleur de lis,(click for larger view)
This necklace is hard to pin down design wise it looks almost ancient, also I think the pearls are a later addition.
Because of the attachment bars and no individual holes for rows?
Also I think it was originally fitted with a choker with maybe silk or velvet that went out of fashion or deteriorated.
It is really puzzling (if only it could speak) lol.
The plot thickens
Thanks Londontown