19th century, Africa
You ask how do we know these are about 100 years old. Actually, they could be older.
At least they have been on land in the hands and hair of people who valued these, trade with these and wore them for beauty and wealth.
And because they have been handled in this way they have the gorgeous patina and warmth you cannot find in the beach shops.
We made the sterling findings in our Santa Fe atelier.
Average shell: 7/8 x 5″
Drop from top of hook: 1.75″