Mermaiden Nouveau Necklace

Is there anything more beautiful?! Art Nouveau era sterling silver necklace with thin box chain attached to a notched bib holding an aquamarine hued pendant framed with intricate wavy lines, stipple dots and a rough freshwater pearl. The centerpiece appears to be a see through shell with bits of iridescent sheen and natural variations. It also looks like it could be a very old and worn out piece of carnival glass, but the grain lines and spots look very organic.

Label: Initials on bib frame, but illegible. 925 Italy (on clasp) - this may be a newer part 
Size: 7 1/2" drop, pendant is 2" wide x 1 3/4" high
Content: Sterling Silver, Glass, Freshwater Pearl
Circa: 1920s, possibly earlier
Condition: Great / light overall wear to the shell and natural patina to the metal, but no actual flaws

• Style No. N251