Fig. 2

Peptide mass fingerprint from samples. a DL157, an indenture concerning property in Bennington, Hertfordshire, signed 20th May 1687. Identified as sheepskin based on diagnostic peptide markers, particularly at 3034.3 (m/z) [25]. b DL189, a tripartite marriage settlement signed 14th November 1737 in Atterton, Leicestershire. Identified as sheepskin based on diagnostic peptide markers. Note the visible erasure of text amending the intended date of the wedding. c DL149, an indenture concerning property in Knaresborough, North Yorkshire, signed 3rd June 1800. While the peptide marker at 2883.4 indicates it is either sheep or goatskin and not calfskin (Bos taurus) the absence of diagnostic peptide markers at 3034.3 (sheep) and 3094.3 (goat) [25] precludes separation of these species (photographs of deeds courtesy of Dave Lee)