Help Identify Silver, Opal, Ivory? Pendant

[mystics_fan]

Hi all,
I'm hoping someone can help me identify & date this unusual pendant. It is hall marked Sterling and has another mark I can't identify. I think the ivory may be real as well.
Thanks in advance,
mystics_fan

[AG2012]

It’s obviously art nouveau style and real ivory (crosshatching of grain lines).
And rather well made, not perfect, though (flaws in stone setting, soldering and casting).
Cannot be European, can it? No ``sterling`` in Continental Europe and British would have full marking.