River pearl or shell?

[A Breaker]

Give it your best guess...what is this? Would this really be a river pearl or is it part of the shell or does that make it a pearl still on the shell? I think it is really interesting, but I just don't know enough.

 

[CortezPearls]

Without a good look at all the sides of the pearl it is impossible to be 100% accurate.
My gut feeling is: Pearl.
Setting looks old fashioned. Any idea of the date of production?

 

[Lagoon Island Pearls]

Without a good look at all the sides of the pearl it is impossible to be 100% accurate.
My gut feeling is: Pearl.
Setting looks old fashioned. Any idea of the date of production?

I agree on all points.

Although only 40% (approx) is visible, the back of the piece presents with features typical in loose pearls.

If possible, I would like to see other images of the rear to substantiate the assessment.

 

[A Breaker]

Thank you so much!!! I wanted this as a "clasp" to lengthen pearls...but wanted a gut feeling from experts....I haven't done much testing on this...it is an old looking C clasp....but that is sometimes used to faux. Thanks again