It was 1965 and the Girl Scouts were having their famous Girl Scout Roundup at Farragut State Park. Idaho was famous for potatoes, but the girls were disappointed because they couldn’t see them growing in North Idaho. As quoted in a 1970 Idaho Statesman interview, Sherlock said that “Idaho First National Bank scraped up some potato banks and gave them to the girls as souvenirs.” They didn’t get pins, though.
Sherlock remembered a pickle company from his childhood that had distributed pickle pins, so he decided to borrow that idea. By 1967, when the World Boy Scout Jamboree came to Farragut, the Idaho Potato Commission was ready with plastic potato pins. They have distributed, conservatively, 2.5 bajillion of them since.