This is a difficult stamp to identify. Guigard attributed it to the Duke of Savoy, but it is almost certainly English. Many of the books went to Cambridge with the library of John Moore, Bishop of Ely, and of these a number have the initials of Henry Lucas, the seventeenth-century English book collector. None of the books I have seen are later than 1639, and the collection must have been sold soon after that. The reason for attributing the arms to Hussey, is that the hatching of the cross in the stamp is that for vert in the system of hatchings introduced in the seventeenth century, but not generally used on armorial stamps until much later. One of the books at Cambridge has the cross painted green, but then another has it impressed in silver. One book has a small version of the stamp on its titlepage, but in that case the cross has been left blank and the field is black. George Smith, and F.B. Benger in A collection of armorial bookbindings (London, Ellis, 1927) p.33 attributes the stamp to Sir Edward Hussey of Honington, who died in 1648. The number of medical works among the known books suggest that it could be the stamp of “Mr John More of London doctor in phisick to his Matie”, who was the son of Edward More of Thellwell in Cheshire, and Alice, daughter of Robert Marscroft of Marscroft in the same county. He took his B.A. from University College, Oxford 23 January 1581, M.A. 3 July 1583, and was licensed to practice medicine 28 June 1596. A Fellow of the Royal College of Physicians, he was returned by the College to the parliamentary commissioners as a Catholic 29 March 1626. He died, a bachelor, at the end of November 1641, and his library seems to have been sold soon afterwards. His arms were Sable a cross argent. However this is very speculative and it is probably better to wait for a book that gives some clear indication of the provenance of the arms, and meanwhile classify it as unidentified.