The archive contains material compiled and created by Simpson throughout his working life, and the majority pertains to his own research on collecting and collections.
Although the records relating to all of the organisations Simpson worked for are of interest, those created and compiled by the London officer of the dealer's M. Knoedler & Company present an extremely rich resource for the study of provenance, collections and collecting. The focus is mainly on British Art, but also includes European Art and, as a significant proportion of these date to the 1920s, they reveal much about the disbanding of collections after the First World War.
As the material in this archive emanated from two sources, records left at the The Paul Mellon Centre and those left at The Barber Institute of Fine Arts, very little of the original order remained. Therefore, during the process of cataloguing the two groups were integrated and the following was carried out:
-material has been arranged in chronological order of Simpson's employment, and sub-collections have been created for The Courtauld Institute of Art, The Barber Institute of Fine Arts, M. Knoedler & Company, and The Paul Mellon Centre for Studies in British Art
-within each of these sub-collections, the material has been sorted by themes and material types, for example Correspondence, Artists, Sitters, Collections, etc. Therefore, as Simpson repurposed records from different sources for his own research, some of M. Knoedler's records may be found in the Collection Files in the Paul Mellon Centre sub-collection.
-black and white photographs created in connection with the buying and selling of works of art have been integrated with relevant written records in the Artist and Sitter Files series within the M. Knoedler & Company sub-collection
-The Paul Mellon Centre's Library Collection files have been integrated with similar material found amongst the Simpson Archive
In order to avoid confusion caused by two individuals with the same surname, Frank Simpson is referred to as Simpson in the catalogue descriptions, whilst his aunt is referred to as Letitia Simpson.