Berkeley’s subject catalogue is already gone. Though it was more or less frozen in the nineteen-eighties, it was nonetheless very efficient for some kinds of searches: if the primary sources in your field were published in the eighteenth and nineteenth centuries, you don’t want your retrievals spread among the thousands of irrelevant records that a mechanical database subject haul brings up. Any drawer of an out-of-date paper catalogue represents the equivalent of a filtered computer search, a Boolean date-limited search, of a very sophisticated sort—in fact, one drawer represents the outcome of a kind of search that most on-line catalogues can’t and won’t ever be able to perform, since it offers clues to what books were in the library during different eras. If in seventy years a historian of science (say) wants to know whether some Nobel-laureate physics professor could possibly have seen and been influenced by a certain out-of-the-way Dutch mathematical monograph from the thirties which bears important similarities to his work—whether, that is, it was part of the library’s collection during the period when the professor was developing his ideas or was acquired only after the professor’s papers were published (perhaps acquired by the library as a gift from the professor’s estate, in fact, because the professor was sent the monograph by the Dutchman himself, anxious to establish primacy)—the historian of science will have little chance of finding an answer to his question now, because the computer record will bear the (to him) meaningless date of the retrospective conversion of the card, i.e., sometime in the late eighties or early nineties, which has no relation to the time that the card was originally produced (and the book placed on the shelf), whereas the original card, even if it bore no direct date of creation, would have exhibited distinct features (typewriter style, format, cataloguing conventions) that might have enabled a cataloguecard paleographer to place it within a five-year Period.
interesting research example of a search not enabled by a digital card catalog