"Deep" as a subcategory of "book"?

#1

An extract from the Bolton MBC Byelaws for Public Libraries and Museums 1988:

(f)“book” includes any and every book, journal, pamphlet, music score, manuscript, picture, print, photograph, engraving, etching, deep, map, chart, plan, gramophone record, film and any other article of a like nature forming part of the contents of the Library or lent to any person by or on behalf of the Library Authority.

Does anybody have any idea what ‘deep’ means in this context? I’ve trawled every dictionary and word reference I have and can’t find anything relevant. Is it a typo? If so, for what?

#2

Typo?

There is a simlilar list of potentially booky type things at the end of p2 here and they also include the word ‘deed’ along with photographs, engravings, etchings etc.

#3

Not only do I think you’re right, that looks like that might be the original paragraph that was altered in transcription. Brilliant find!