From John Fisher's collection, lot 42.
This is an envelope (with price in UK currencly, perhaps sold by Corinda or Magic Wand) containing two sheets (one letter size, probably an Annemann's original, the other a typed copy) of the "Test of the Tiber" book test. This is a very clever "telephone book" test, where two spectators write (apparently) a page number and a line number and the magician divines the name on that line. The method uses billetts, an Annemann's favourite, and a clever construction. A very clever book test, not impromptu.