Patents, trademarks, and copyrights. Part1:Rules of practice in patent cases. Section1.5:Identification of patent, patent application, or patent-related proceeding.
(a) No correspondence relating to an application should be filed prior to receipt of the application number from the Patent and Trademark Office. When a letter directed to the Patent and Trademark Office concerns a previously filed application for a patent, it must identify on the top page in a conspicuous location,