Sterling pin, any idea on age, maker, value, and type of stone?

[Bitdrop]

Picked up this pin at a pawn shop for $10. It's stamped sterling and has a large stone set in it. I'm not sure what the stone is - if anyone knows chime in. It's fairly large and has a lot of tarnish. Any idea on age, maker, or value?

 

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[tamrock]

Well the mark looks like a copyright stamp. It is a one off 1970's ?? modernist studio art piece imo. The stone may be some kind of brecciated agate I'm guessing?. I could see someone who collects unique jewelry, giving maybe up to a hundred bucks on it? Who knows, maybe even more on the right day It at least caught your eye and that's a good indication of it being desirable.