It occurs to me that there are a few things - like the Parma Magica - where it would be very useful to have books available, such as a summa that will get you up to 3 ASAP if you want to Parma both a teacher and an apprentice, but where having books around risks letting stuff out of the Order.
So, my thought was, what about an encryption scheme that requires Hermetic magic to read?
So I came up with the following spell:
Rightful Seeker of Hermetic Knowledge
InTe(He) Level 35
This spell automatically decodes a specific cypher, chosen when the spell is learned(if the cypher is not pre-selected by the teacher or the text, the rules for it must be available while the magus is learning the spell). The meaning of the cyper is revealed effortlessly to the magus for the duration of the spell, permitting the study of texts using the cypher to conceal their contents.
(InTe base 4, +2 Sun, +4 Vision, +1 He requisite)
The cypher itself should be designed to be as hard as possible, and maybe also incorporate knowledge specific to the Order(like Magic Theory and Order of Hermes Lore) to make it really, really hard for outsiders to break the cypher mundanely.
For people who aren't InTe(He) experts, or who might be worried about the potential for warping from over-study, I imagine that a lens could be enchanted to do much the same thing, although in such a case it should have a linked trigger restricting it to members of the Order who haven't been Marched or something similar.