US Patent Numbers
United States patents date back to the late 18th century, but the patent office was burned down during the war of 1812. The patent office reopened in 1836 with the number “1” as its first patent number, even though information on a handful of earlier patents dating back to 1790 still exist. In 1843, the patent office began to issue design patents. The first number issued was “D1”.
Patent numbers are frequently found on decorative antiques, giving an indication of their age.