At one time the category 'Ancient Documents' was included as a subcategory of 'Calligraphy and Books,' but beginning in 1985, 'Calligraphy and Books' and 'Ancient Documents' were separated into two distinct categories; this new distinction was then retroactively applied to all the items formerly designated national treasures, putting each into either the 'Calligraphy and Books' or the 'Ancient Documents' category.
かつては古文書類も「書跡・典籍」の部に含まれていたが、1985年（昭和60年）度から「書跡・典籍」の部と「古文書」の部は別個に指定されるようになり、既指定物件についても「書跡・典籍」と「古文書」とにあらためて区分されている。