The Cipher Manuscripts are about sixty folios of loose leaves, written in a substitution cipher, containing the skeleton of a magical order: outlines of grade rituals, the grade structure itself, and lists of correspondences. They are outlines rather than finished ceremonies, terse to the point of being notes, and the elaborated rituals the Golden Dawn actually used were built out from them by Westcott and Mathers.
The cipher is the detail worth dwelling on. It is a simple substitution taken from a published work of Trithemius, printed and available in the British Museum, and it can be broken by anyone who recognises the source. A genuinely secret document would not use a cipher out of a library book. That has been read two ways: as evidence the manuscripts were never meant to be secure, and as evidence about who assembled them and how recently.
The papers were accompanied by correspondence with a German adept named Anna Sprengel, said to confer authority to found a temple. No trace of her has ever been found outside those letters, the addresses do not check out, and the German is poor. The atlas records the charter as forged and the manuscripts themselves as an open question of a different kind.