Refers to one of 2,845 early US patents whose records could be restored after the Great Fire of 1836. In 1836 the United States had issued some 10,000 patents; the total number is uncertain because on December 15, 1836 the then US Patent Office, housed with the General and DC Post Offices was destroyed in a fire, along with all records. The fire involved an almost comic level of incompetence, with employees discovering that a fire station and engine in the building was inoperable, with rotten leather hoses and rusted solid pumps after 16-odd years of no maintenance. The numbers of those patents that could be restored after the fire have an X-prefix. Sadly, the Patent Office learned little and although it moved to a fireproof building, many of its records and precious models (at that time models of inventions were often required) were destroyed in a fire on September 24, 1877. As a result a lot of valuable technological history was lost.