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 date 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 for the design. Inventors often marked items in this way even though they had not received, or even applied for, a patent. This was an attempt to discourage others from copying their design even though they had not applied for or had 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. However, the British patent numbering system and the manner in which patent registration was displayed on the item is much more complex than the American system.

British Patent Numbers

Because there was never a set rule for how to cite a British patent on an item, many variations can be found. On older items, often only the name of the inventor or the company was used. Some items show application numbers even though the patent was never granted. A patent

number and year may be listed, or only
a patent number.

British patents were not issued numbers until October 1852. Numbers were then issued retrospectively back to 1617, as
well as forward from that time. It is highly unlikely that an item made prior to 1852 will have a patent number on it.

Dating a British clock based on its patent may be difficult, but it can be done. More information on the British patent numbering system is found at the British Library’s Patents Information section.

British Registered Design Numbers

British registered design numbers are often confused with patent numbers, but they are not the same. A registered design is more like a type of copyright than a patent. They could be used by manufacturers, retailers or designers. An item protected as a registered design may be marked "Registered", "Rd." or "Reg. Des."

From 1842-1883, registered design numbers were written within sections of a diamond shaped form, with with letters and numbers at each corner giving information about the registration date, type of material, etc.

In 1884 the system was changed to a sequential numbering system. This chart can help you determine the earliest year in which a registered design number was issued.