In 1771 the antiquarian Alexander Thistlethwayte gave around 1,500 books to Wadham College. Four years previously he had made a similar donation to Winchester College, and both donations include books that Thistlethwayte marked up with what is apparently a code. Dr Geoffrey Day, Fellows' and Eccles Librarian at Winchester College, writes (especially for this exhibition):

Alexander Thistlethwayte gave Winchester College a large number of books in 1767. College records claim that there were 3,500 volumes in the gift, but the recent revision of the catalogue suggests a number nearer to 1,500. They include books in English, Latin, Greek, French, German, Dutch, Spanish, Italian and Arabic. Over 100 of the books are marked with codes, which remain undeciphered. A number of patterns recur: ‘Billiod’ being found as the first sequence on several volumes. Often an alphanumeric sequence, the length of some, like utility bill customer references, is quite baffling. Why would one need a 17 character code?

Image 1 from: Pierre de Lenglet, Carmina, Paris, E Typographia FRancisci le Cointe, 1692

Image 2 from: Johannes Surius, S.J., Moratae poeseos, Atrebati Regiacorum [Arras], Typis Gulielmi Riverij, 1617, 2 vols in 1.