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Detailed, authoritative guidelines set forth for the creation, development, and administration of the U.S. Patent Classification (USPC) system are contained in the document entitled Development and Use of Patent Classification Systems (DUPACS), published in January 1966. Refer to DUPACS for more comprehensive information about the general practices and procedures outlined herein.

The USPC system provides for the storage and retrieval of every U.S. patent document that a patent examiner needs to review when examining patent applications. Therefore, in the aggregate, the system must be exhaustive of all patentable subject matter under patent laws. Although the system is primarily designed to assist patent examiners performing patentability searches, the system is used by a wide variety of other users, e.g., patent attorneys and agents, people involved in research and development, and the patrons of the Patent and Trademark Depository Library (PTDL) system.

The present USPC system reflects the uneven growth derived from the first general scheme created in 1900. Classification before 1900 closely paralleled economic groupings of the period with informal and arbitrary subdivisions to provide manageable size collections. Relationships among such patent collections, if they existed, were lost in the alphabetical ordering of titles assigned to each of the collections. Search notes, class and subclass definitions, or schedule explanations either did not exist or, at most, were primitive.

While all of the present major groupings have been “revised” since 1900, each class reflects the theories of classification that existed at the time it was reclassified. The guidelines set forth below are generally applicable only for classes revised since 1940. The location of the “miscellaneous” subclass (if a class includes such a subclass) is an indicator of the age of any class. For example, if this subclass is placed in any location other than as the last subclass in the schedule, it can be assumed that the class was reclassified before 1940. For further information on the original distribution date of any class, refer to the Manual of Classification, pages CP-1 et seq.

This handbook is intended for use by U.S. patent examiners. There are two other condensed handbook versions of DUPACS. They are entitled “Handbook on Use of the USPC System” and “Handbook on Use of the USPC System for Patent and Trademark Depository Libraries” and are available for other users. This handbook is based on and draws heavily from the “Guide to the U.S. Patent Classification Systems,” issued in June 1973. We are indebted to its author and authors of earlier publications on patent classification for much of the useful information that has been reproduced in this handbook.

The authors wish to thank the many people who read and commented on this handbook. Their comments were integrated into this publication. It is hoped that this handbook will provide system users with a clearer understanding of the system, its use, and its administration.

Authored by: Edward Earls, Harold Smith, Leslie Wolf, Robert Saifer, Edmond Rishell, Diane Russell, Charles Rademaker

Updated November 19, 1997, by Ray Rush and H. Kilby.
Chapter VII, added February 1999, authored by Charles A. Rademaker.
Updated May 2003 by Dave Bender.

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