As the examples show the nationality of the patent is not always indicated. The number itself, together with the probable date of invention or manufacture, can often provide a clue as to the nationality of a patent since numeration often varies widely from country to country. The table below gives the years for selected countries when patents began to be published in that number range. A concordance to American utility patent numbers is available for reference elsewhere on the web. Patent numbers have increasingly applied only to one or more aspects or parts of the artefact, rather than the artefact in its entirety.
Pocket calculators are good examples.
In addition, there may be several patent numbers relating to the artefact. Table showing highest application number in each year, 1852-1915 British patents granted during 1617 to September 1852 were not numbered at the time, and were only retrospectively numbered in the 1850s. Artefacts are extremely unlikely to have a number if they date from before 1852. From October 1852 to 1915 patent applications were consecutively numbered within each year, and if published retained the same number. The table below gives the highest number attained in each year as some patent indications do not state the relevant year, and knowing the number ranges help eliminate possibilities.