Patent Specification Descriptors: "type" or "kind" codes
Most patent-issuing authorities issue more than one document for any particular patent. These sequential documents often keep the same number, so they are distinguished by adding a letter immediately after the number. This system originated in West Germany in 1968, when codes were used to distinguish between three document types:
These codes were also given a numerical suffix to indicate the number of times the specification had been published (e.g. A1, B2, C3).
Today, as many applications reach the acceptance stage before the examined document is published (18 months after filing), the second publication stage is avoided, and the granted patent document is given the code C(=granted status)2(=second publication).
Derwent World Patents Index originally catered for only a single alphabetic character (A, B, C etc,) as a suffix for patent numbers. This was subsequently expanded to include the full suffix, so the patent's publication sequence could be understood. Earlier files were however not updated with this information.
In some countries, including the USA prior to 2001, usually only one document is issued so there is only one suffix for published patents from that country. Granted documents from other countries may be given a different suffix.
Occasionally, Thomson Scientific has created status codes unique to our own services. For example, as Germany is a signatory to both the EPC and PCT, applicants pursuing either of these routes for patent protection may designate Germany as one of the countries in which protection is sought.
After examination by the European Patent Office (for EPC) or by WIPO (for PCT), the applications will then pass to the German Patent Office for issue in the normal way as a domestic patent. Those entering from the EPO are given the suffix G in DWPI, whereas those from the PCT receive the suffix T (for Transfer). For documents which transfer from the EPO to Germany in other languages (French or German), we add the suffix E.
Although in general suffix letters follow similar meanings in different countries they are not identical, and you are advised to check them.