One with a laser welder can repair it.
Take it off with #000 steel wool. Use any of these post for protection afterwords. https://www.bladeforums.com/threads/mammoth-ivory-care.521168/
Broken solder joint,it's hanging on the backside.
A vesta is a match holder with striker,yours is a permanent match.
United States Air Force USAF Master Flight Nurse Wings
Air medal.... https://airandspace.si.edu/collection-objects/medal-air-medal/nasm_A19630421000
Eight rows down is a close example of yours .... https://www.morninggloryjewelry.com/articles/gallery/snakes-serpents/
Is there a photo of the back side? It looks like the tail would be at least 30mm too long.
Take another look.... standard rat tail.
Looks like a rat.
https://www.google.com/search?q=bone+sewing+bodkins&tbm=isch&ved=2ahUKEwj86ZvCvJ_5AhUSkGoFHdgjB7wQ2-cCegQIABAA&oq=bone+sewing+bodkins&gs_lcp=CgNpbW...
The center stone and several others are no older than 1920.
Looks like blue chalcedony.
Amazonite can have cross hatching,see photo here....https://geology.com/gemstones/amazonite/
Photos?
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