The 973 pin is a symbol used to represent America.
The number is a reference to a system of classifying items in a library devised by Melville Dewey. In this system, numbers in the 900's represent history and biographies. Numbers in the 970's represent the history of North America. And 973 is used to classify items under the history of the United States of America.
A set of 100 of these pins were commissioned on 24 April 2019.