I offer a collection of more than 200 patents of the inventor Freeman Harrison Owens (USA), published between 1916 and 1962 in the USA or Great Britain (> 190 patents, in english), Germany and France (in german resp. french). Most of the patents are busy with cameras / film cameras / sound film apparatus or parts of it and other photographic items, in later years partially also for televisiopn technique and some other topics.
All patents are complete, that means contain the full text and all drawings (see example). You will get a professional overview about the technical developments of Owens which you find nowhere in the world in this good quality / completeness. You can learn a lot about the technical details of old camera / photographic technique.