Dating American Clocks by Their Patent Numbers
Parts found in many American clocks may be marked with one or more United States patent numbers. This chart will show you the earliest possible date an item marked with a patent number could have been made.
Sometimes you may find a part with just a patent date but no number (such as “Pat 1795”). Such a patent date does not always mean a patent was actually issued. Inventors often marked items this way to discourage copying even though they had not applied for or been awarded a patent.
Dating British Clocks by Their Patent and/or Registered Design Numbers
Parts found in many British clocks may be marked with one or more British patent numbers or registered design numbers. British patents were not issued numbers until October 1852. It is highly unlikely that an item made prior to 1852 will have a patent number on it.
British registered design numbers are often marked “Registered”, “Rd.” or “Reg. Des.” From 1842-1883 they used a diamond-shaped mark; from 1884 onward a sequential numbering system was used.