I would NOT use a piece of copper wire as a pin on an ivory handled knife....unless you really want to cuss a lot. The copper will stain the ivory badly when sanding and polishing.
Good story;
A preacher had just moved into the manse at his new church. He was walking around the neighborhood and saw a boy sitting by a lawnmower with a "For Sale" sign on it. He asked the boy why he was selling the mower, and the boy said his dad gave it to him when he bought a new one, so he wanted to sell it an get a bicycle. The preacher said there was a bicycle in the garage at the manse, and he needed a mower, so why didn't they trade. The boy said yes and the preached went back for the bike. As the boy was riding the bike up and down the street, the preacher tried to start the mower with no success. He asked the boy how to start it, and the boy said , "Dad just pulls the rope hard and cusses at it real loud." The preacher laughed and said he didn't know any cuss words. The boy grinned and said, Yeah, my dad didn't either...until he got that mower.