Edward Oliveira of Newport, Rhode Island was granted a patent (#2,749,555) in 1956 for a "date hat". His idea was that, by wearing the hat, a young woman could display whether she was available for a date on a specific day. From the patent:
In high schools, colleges and the like, it is often impossible to carry on very much of a conversation during, or even between classes. Since many dates between boys and girls are most easily made when they are gathered together in school, it is a disadvantage not to be able to tell whether a girl is already dated for a particular day and hour. If a boy knew that one girl is already dated for the particular time he desires, he would quickly be able to attempt to date another girl who was not already dated. However, up to the present time, this has been difficult because, in many instances, there is not sufficient time to talk to every available girl to determine their date status. In order to remedy the above situation, it is one object of the present invention to provide an article of wearing apparel which can be set to indicate to any observer whether a girl has a date for the particular time desired.
I can see a problem with this concept. Would a young woman really want to publicly display that no one had asked her out?
Also, had Oliveira attempted to get dates by systematically asking out every girl in his school? Thus leading to his frustration that there was "not sufficient time to talk to every available girl to determine their date status."