Antique Gold and Pearl Necklace

This chain and pendant are quite old. The clasp of the chain is unusual in that you need to use your fingernail to pull on the raised part in order to open the clasp. The bale of the pendant too is unusual...first I've seen of this type (lots of photos). Including the pendant, it measures 19 inches. I believe the pendant is gold plated over silver and the chain is gold-filled though neither is marked and this is my educated guess.