If a product proves popular with consumers, suppliers are encouraged to provide more of it. This has often happened with coins and currency sold to collectors.
A notable example of that happened in America in the 1930s. In 1936, the U.S. Mint struck 33 different commemorative silver half dollars among 19 different themes and different mintmarks. There were a number of other proposed commemoratives for that year that never went into production. In reaction to this plethora, future issues dwindled. After 1939 there were only issues in 1946 for Iowa’s Centennial, from 1946-1951 for Booker T. Washington, and from 1951-1954 for George Washington Carver and Booker T. Washington.
After that,
