Pen case, steel and gold, Tibet, 15th-16th century AD
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https://media.piefed.social/posts/67/o1/67o1fNPnQaUj7FG.jpeg
https://media.piefed.social/posts/67/o1/67o1fNPnQaUj7FG.jpeg
https://www.peterfiner.com/artworks/item/2945
It would probably store pens of bamboo or reed like these: