Showed mine to a 70 year old friend/smithy who has been working on guns since he was 11, said, "Heard of them but never seen one." (He is now gone.

) Still haven't found anyone else who has ever seen one, let alone worked on one.
Suggest either finding someone online - chancy... or go to a smithy you know and trust that likes unusual items, see if he'll look at it or take it on as a rainy day/some day kindof thing.
But then, maybe soneone on here knows about them?
Though defensive violence will always be “a sad necessity” in the eyes of men of principle, it would be still more unfortunate if wrongdoers should dominate just men. - St. Augustine