Patent classification systems

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There were many patent classification systems, varying over time, and varying between nations in the manner and the timing of their evolutions. To the present-day researcher, working at least largely online, and interested in finding antique patent material, international/global systems are of note in their retroactive projection of later international classifications onto antique, and national, patent material. Contemporary national patent websites, when they exist, vary in their overall quality and in terms of their active interfacing with the below-mentioned international/global systems and with the international websites through which we may gain at least a partial overview. All of this affects our manner of gathering data and in some instances it affects the manner in which we ultimately determine the antique patent classifications which were nationally applied.

To varying degrees, and sometimes fairly ambiguously, the patent classification system of one nation would affect that of another.

Usage of the word “patent” itself slightly varies in the evolving and internationally variable context of what we may call “administrative culture”.

International/global systems

  • the CPC category system is the most modern and global, started 2010
  • the IPC is the predecessor to the CPC, started 1971, per Wang (2018)[1]
    • IPC1-7 - an IPC version or variant
    • sometimes there are specific references to the 2006 or other dates of one of these

National systems

These are generally contemporaneous relative to the antique material we examine, with the classifications being contemporaneously applied, and visible on the the original documents. Among exceptions are the USPC and the odd case of Dutch patent classifications, in which latter case the antique classification affects a much later process of digital interfacing. In both cases we are dealing with types of nationally retroactive classification.

  • Australian patent classifications
  • Austrian patent classifications
  • Belgian patent classifications -- This is tidy, at least in the aggregate, an evolving system which we can trace from its most raw and perhaps never completely standardized beginnings up through the two distinct and well-standardized stages which bring our data up through 1916. A category system appears to exist around 1830, with numbers like BE 9 and BE 11. They seem to be evolving over time. We don't know if they were on the patent specifications. The key later category is BE K, defined as pertaining to “Navigation, Pêche, Aérostation”. In our experience, toward the latest patents we have accesses, the results are roughly half aero, and with the the overwhelming majority of Belgian aero-patents falling within this BE K. A minority of contemporaneous Belgian aero-patents fall withing BE J and BE L.
  • British patent classifications -- Woodcroft developed a system in the 1840s? and we think it was used in the office quickly
  • Canadian patent classifications -- seems to look a lot like the USPC but the history of it is not known yet ; it was used till circa 1989
  • Cuban patent classifications -- This is new to us, and thus far drawn from antique source material, possibly captured in an evolving state comparable to that of the furthest antique Belgian material, for instance ; thus far we've only seen indications of puerly phrasal-descriptive, rather than numerical or alphabetical, means of differentiating between types of patents.
  • Danish patent classifications -- same as German so far as we know
  • Dutch patent classifications -- Regarding aero, we have a fairly tidy grasp on this. "Klasse 62" covers both aviation and LTA. This "Klasse" is composed of "Groeps". This is an interesting case in which a late patent office founding led perhaps to an unusually modern-practical "early" national system, with no patchy evolution of aero-classification starting as a subclassification of marine, for instance, also interesting in that antique national classifications have been retroactively applied, in the manner of IPC and CPC, and somewhat in the interest of interfacing with these, most particularly as well the antique "Klasse 62" is retroactively and digitally used as a means of culling all the patent data found within that Klasse's "Groeps" ; the further-narrowed antique and national classification being sought is then determined by way of viewing the original, largely by way of Espacenet, after the patent or patents have been found. (We currently lack the outline of patent classification going beyond aero.)
  • Finnish patent classifications -- same as German so far as we know
  • French patent classifications -- dated in 50-year groups from 1853-1904 then from 1904-1958
  • German patent classifications -- starting 1877-8, had the highest examination standards; until further notice this system was also used in Norway and Finland
  • Hungarian patent classifications -- This is very tidy. We have the broad outline of classifications, going beyond aero, with “Főosztály V” (which goes into railways and machinery more broadly) being a rare case in which a national aero-patent classification evolved from a pre-existing land-travel-based, rather than marine-based, broader classification. “Osztály V/h”, our HU V/h, seemingly contains all and only aero-material. We have modern hearsay indicating that this system was "based on the German"; the "h" in HU V/h vaguely comports with this, though in the Hungarian case said "h" seems to zero down into the narrowest classification.
  • Italian patent classifications -- IT 8 is the relevant class for aviation
  • Luxembourgish patent classifications -- not yet established but we have examples
  • Mexican patent classifications -- 1903 system is plain, with a couple of levels above the substantive subclasses, in the French/Belgian style.
  • Norwegian patent classifications -- like Germany's, possibly with variation
  • Russian patent classifications -- a small number of groups, with RU Group V seeming most related to aeronautics, shifting c. 1910 to a system closer to Germany, the Netherlands, and Scandinavia, with RU 62b used for aeronautics. See also Soviet patent classifications.
  • Spanish patent classifications -- We have extremely little, or nothing, on these. Patent originals are hard to come by, and Spanish participation on Espacenet is numerically decent but qualitatively quite minimal indeed, and we have not accessed antique catalogues.
  • Swedish patent classifications -- include examinations starting 1884; only US and DE were doing that already
  • Swiss patent classifications -- There was a classification system of 1888, then one in 1890, and one in 1908. We have near full documentation on the later two
  • US patent classification systems -- Changed frequently over time

Comparative treatment of patent classes and patent subclasses across the international context

We are following the evolutions of national systems. In the cases of some nations, at some points, the evolutions were fairly subtle. In other cases, a new system was instituted as a replacement of an earlier system. In general, these evolutions had to do with the handling of larger and more precisely varied aggregates of information, reflecting the ongoing elaborations of technology.

Patent classes

Examples include :

  • Classe, French
  • Klasse, German, and Dutch, and other
  • Catégorie, Belgian, numbered Première through Septième, then later alphabetized A-S
  • Főosztály, uniquely Hungarian

Patent subclasses

There is actually an evolving process going into further degrees of subclassification. That is, we find subclasses within sublasses, with varying alphabetical and numerical elements being used in alternation.

Examples include :


  • In the scan of Patent FR-1902-325343 we have an instance of classifications by the German office written onto their copy of a French patent (albeit a member of an international family of which a German version probably also existed and required classification).
  • We have rare instances of patents being classified, in print on the original patent document, with the same said classifications being pencilled over. Instances include Patent DE-1905-175477‎ and Patent DE-1906-175478‎. At present we don't know whether or not these or any fraction of these were a “corrections” which were ultimately retained.


  1. Wang, 2018, Patent Classification Systems, p. 2: "The IPC was established in 1971 by the Strasbourg Agreement, a treaty administered by the World Intellectual Property Office (WIPO) in Geneva, Switzerland, to provide alphanumeric symbols that divide patent subject matter into eight groups with about 70,000 subgroups (WIPO, 2018). Youngest among the three systems and developed based on the IPC, the CPC was initiated in 2010 as a partnership between the USPTO and the European Patent Office to harmonize their existing classification systems (CPC, 2013)."
Enclosing categories Techtype
Subcategories CPC, IPC, IPC1-7, Australian patent classifications, Austrian patent classifications, Belgian patent classifications, British patent classifications, Canadian patent classifications, Danish patent classifications, Dutch patent classifications, French patent classifications, German patent classifications, Hungarian patent classifications, Mexican patent classifications, Russian patent classifications, Soviet patent classifications, Swedish patent classifications, Swiss patent classifications, US patent classification systems, USPC
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