You make two very good points. I think I will change the first sentence to "The binding of red leather with gilt tooling is post-medieval." until we have a more specific date.  I see your point on the word prefatory. Can you suggest a better term to cover the all of non-biblical texts and tables that were included with with early Gospel Books (Jerome's letters, the canon tables, name lists, the various prologues and arguments, etc.) Perhaps "explanatory" might work. I do think that the fact that the prologues are gathered together in the beginning should be mentioned since in many of the other insular manuscripts they are not.