1923 Harding Memorial Set
U.S. #610 was a special stamp that was to be issued for a limited time of about 60 to 90 days in memory of Warren Harding, the 29th President of the United States. Harding had collapsed and died while in office. Of the 200,000 copies sent to Marion, Ohio (Harding’s hometown), 180,000 were sold the first day of issue.
Demand for this stamp was far greater than for any previous special issue. It was impossible to meet the demand by printing from flat plates alone. The Bureau of Engraving and Printing was finally authorized to supplement that printing with a rotary press version. This was the first commemorative or memorial stamp issued using two printing methods. Eventually, over one billion stamps were issued, stretching the original 60-day limit to nearly 6 full months.