Includes primarily research notes, correspondence, copies of original and published material, and images collected and created during research for the Mercier catalogue (Ingamells, J. and Raines, R. A catalogue of paintings, drawings and etchings of Philip Mercier. Annual volume of the Walpole Society, Vol 46, 1976-1978, p.1-70). Most of the images are anotated by Ingamells.
Also includes a considerable amount of material compiled post-publication, including further research, photographs, opinions correspondence, an annoated copy of the published text, and a list of addenda to the catalogue created by Ingamells.