For series that were issued with dust jackets (DJs), clues to the vintage in the form of listings inside the book and on the jacket can be compared. Often the listings in the book change less frequently than those on the DJs because of the size of the print runs for each. It is normal for there to be a slight variation of the last title listed on the book vs. DJ. Usually the last title on the DJ will be no more than a book or two beyond any inside list.
Lists of titles on the copyright page of a book (back of the title page) usually do not change so should not be used as a dating guide.
If the listings on the jacket are widely different from the book listings, the book and jacket may be said to be a “mismatch.” For series where there are detailed bibliographic format guides, such as Farah’s Guide for Nancy Drew or Hardy & Hardy Investigations for the Hardy Boys, these guides can be used (with practice) to identify mismatches.
A mismatch can occur for innocent reasons. Some anecdotes of booksellers who offered the books new relate how the jackets were stored in a drawer behind the counter and browsers could select among the jacketless copies on a shelf or table. When the book was brought up for sale, a jacket matching the title would be placed on the book from a drawer.
More often, however, a mismatch occurs when a collector or bookseller is trying to enhance a given copy. They may take a nicer condition and newer jacket and place it on an older copy of the same title.
For most collectors, a mismatch is a book that they will wish to replace at some point. Many collectors avoid them so a mismatch often has lower resale value.
A common mismatch still found among collections and sale inventory was to take the brighter dust jacket from a mid-1932 or later orange cloth copy of Tom Swift and His Giant Magnet (1932) and place it on the earlier format tan cloth book with the quadrant design stamped on the cover. The mismatch combination is worth considerably less than a proper match for either format. Sometimes this was a collector who wanted something nice on the shelf and knew little of the risks of mismatches. It can also occur for someone trying to make a more valuable combination for the tan format with a proper dust jacket.