This project aims to present a complete survey of all the surviving correspondence associated with William of Orange (1533-1584). The term correspondence is used in the broadest sense and includes not only letters that were sent to or written by William of Orange, but also commissions, petitions, instructions and speeches. Research for this project was carried out in almost 200 archives and libraries in the Netherlands, Belgium, Denmark, Germany, England, France, Italy, Austria, Poland, Spain, Vatican City, Sweden and Switzerland.
So far, 12,609 documents have been found and the oldest letter dates from 1549. Key information on every single letter has been stored in a central database: the date it was written, the correspondent, where it was sent from, where it was found, the type of document (letter, speech, etc.), and a brief description of its contents. Photographs were taken of most of the letters and documents. The films and copies were then scanned and the scanned images saved in a photo database. A link has been created between these digital files and the unique identification number assigned to each letter in the database.