Newbie in search of advice

[NinjaSkittle]

Hello all! I'm new here and a while back I purchased some jewelry from someone that claimed the pieces were dated somewhere in the 1970's, I'm wondering how to tell if I was ripped off?
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[Bron357]

The photo of the first piece is too hard to see what it is "paua shell? perhaps. Are there any numbers ie 925 (sterling silver) or 9,10,14,18 k or c (for gold) on the metal ? The second item contains a genuine white Australian opal and should be set in sterling silver or possibly white gold.