To me, it looks like someone has made a brooch from the pectoral spine from the granulated catfish, Pterodoras granulosus.
I may be wrong and I'm sure someone will correct me if I am.
I agree. We had a pectoral fin spine last week but were unable to assign it to a species. I think this is more doable and here is an image of the fin spine in life: http://www.planetcatfish.com/catelog/image.php?image_id=8269
Interesting how it is visible although covered with some skin/flesh - makes them pretty formidable.
I can see how you would make that mistake but may I draw your attention to this URL?
I'm sure if you look closely you will see how much closer to the original pictures this is, also look at the spacing between the "Teeth" on the Saw Fish, the gaps are much greater than those on the original specimen.
Then there is the size, a sawfish is a much larger creature, even the rostrum (saw) on a baby is much larger than the specimen in the original post, being around two feet in length at birth.
You can see the structure displayed quite clearly within the pectoral fin in the Image below
I'm sticking with my original ID the pectoral fin of the granulated catfish, Pterodoras granulosus