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by codazoda 1912 days ago
Apparently these are called a "paper clinch".
1 comments
Animats 1912 days ago
There are crimp-type devices, and there are ones that cut a slot and tab. The slot and tab devices were patented in 1910. The main one was the "Bump Paper Fastener", which shows up on eBay now and then. So that's automatic letter-locking.

[1] https://pdfpiw.uspto.gov/.piw?docid=01065904&

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