This chapter highlights some of the work, selected either because of its originality, or because it is – probably – representative of broader practice generally. In either case, the theories and practice of classification and arrangement deserve examination given that, from the beginning of the seventeenth century onwards, Europe was divided by its adoption of two major systems of archival administration. Originality and eccentricity sometimes predominated in the world of archival administration. The chapter highlights some particularly strange examples, dating from the end of the Middle Ages. The dissemination of archival methods occurred as individual archivists moved between institutions, ordering and arranging the archives in each one. The most widespread archival numbering system in Europe from the fifteenth to the beginning of the nineteenth centuries was a purely numerical one or sometimes alphanumeric. Arabic numerals were preferred for convenience over Roman numerals.