Why most Zippers have the letters YKK on them.
Whitcomb L. Judson invented the zipper and YKK is the Japanese company that makes them.
Whitcomb L. Judson was a lover of gadgets and machines and the idea for his "clasp locker" came from when a friend had a stiff back from trying to fasten his shoes. Judson's clasp locker was used mostly on mailbags, tobacco pouches and shoes. However, his design, like most first inventions needed to be fine-tuned.
A more practical version came on the scene in 1913 when a Swedish-born engineer, Gideon Sundback revised Judson's idea and made his with metal teeth instead of a hook and eye design. In 1917, Sundback patented his "separable fastener."
The name changed again when the B. F. Goodrich Co. used it in rubber boots, galoshes, and called it the "zipper" because the boots could be fastened with one hand.
The 1940s brought about research in Europe of the coil zipper design. The first design was of interlocking brass coils. However, since they could be permanently bent out of shape, making the zipper stop functioning, it was rather bad for business and wasn't too practical. The new design was improved after the discovery of stronger, more flexible synthetics. Coil zippers eventually hit the market in the early 1960s.
In 1934, Yoshida Kogyo Kabushililaisha was founded. Sixty years later they changed their name to YKK Co. The privately owned firm, headquartered in Japan, now is made up of 80 companies at 206 facilities in 52 countries. Wow! you say? but of course, the demand for zippers is great. YKK makes everything from the dyed fabric around the zipper to the brass used to make the actual device.