When Was the Paper Clip Invented?

People used to pin their papers together, of which the needle hurts the paper and the user. A Norwegian inventor named John Waller thought the problem can be solved by a wire paper clip, for which he got a patent in 1901. At almost the same time, several inventors came up with several similar designs.
However, all these solutions had some problems. First, the end of the wire stuck into the paper when it was pushed, causing more damage to the paper than that with the needle. Then, difficulties arose in developing a machine producing clips, as well as the hand-made clips to be much more expensive.
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