The Zipper Cup.

The modern interlocking zipper was perfected in 1914 by Swedish-born Gideon Sundback. "Sundbäck developed a version based on interlocking teeth, the "Hookless No. 2", which was the modern metal zipper in all its essentials. In this fastener each tooth is punched to have a dimple on its bottom and a nib or conical projection on its top. The nib atop one tooth engages in the matching dimple in the bottom of the tooth that follows it on the other...