In the 1950s and 1960s with the improvement of plastic manufacturing techniques, promotional items including keychains became enhanced unique. Businesses could place their names on promotional keychains that were three dimensional for less excessive than the standard gather momentum keychains.
Keychains are small and inexpensive enough to become promotional difficulty for mythical national companies that might give them out by the millions. For example, with the launch of a new movie or television show, those companies might partner Promotional Keychains with food companies to provide a character keychain in each box of cereal etc.