J. McRee Elrod wrote:
<snip>The purpose of single main entry in a physical catalog was purely mechanical. If you have a single card for a single (or at least a complete) resource, and you do not have to write out additional cards by hand but have a mimeograph machine or something, matters were much simpler.
There is nothing in the physical form of the card catalogue to prevent more than one main entry, if the shelf list card were used to record entries as opposed to the main entry card; main entry is only a matter of unit card indentation, and two or more enties could could share first indentation, being ticked for filing.
But if you have a longer record that needs more cards and has more complex holdings, then matters are different. Through the magic of the Internet, I have managed to find a real example, although it's in Russian, but that is unimportant.
In Princeton's scan of their card catalog, we can see the main entry card for Marx & Engel's complete works in Russian. http://tinyurl.com/67jo35c It gives the extent 50 v. in 54. If you go to the next card, there's a dashed-on for an index published in 1974.
When we look for the AE card under Engels http://tinyurl.com/5tblcjb we see it lacks the extent statement, and there is no second card, with no notice of the other index.
When we get to a subject card http://tinyurl.com/6gn7zsa, it's also a single card, so you don't know about the other index, plus, there is the stamp: For Holdings see Main Card (which I guess people understood back then).
Also, when comparing these cards, the ME card had more extensive information about the AE cards. Finally, reading a bit more closely: this bookset started in 1955 and ended in 1981, so there was probably a lot of work done *in pencil* with temporary holdings throughout the years, and changed to pen at the end. Also, this card came originally from LC, cataloged by them in 1956, and was originally a single card. The second card was a locally typed one when the second index came out, and they stamped "See next card" on the LC card.
In a card catalog, they wanted above all to keep the number of cards to a minimum so the catalog would not get out of control, this is why AE cards were limited to single cards. Plus, just looking at the physical labor the ME card above shows, to copy that same information for, e.g. in this case, holdings in several different places, plus the shelflist and maybe even an official catalog, if you had one, was just too much work and begging for errors.
(I can't hold myself back from mentioning what appears to be a "correction" from the reviser, or at least some kind of a change. The original cataloger wanted to add a card under the title of this book in Russian (Sochineniia) for Karl Marx, but it was crossed out. Whether this happened at the time of cataloging, or this card was withdrawn later, I don't know. But the final result is rather confusing: you can find this book under Marx, Karl, 1818-1883. Works. Russian (the ME card), but not under the book's title "Sochineniia", whereas you *can* find this book under Engels, Friedrich, 1820-1895. Sochineniia, but *not* under Engels, Friedrich, 1820-1895. Works. Russian, exactly the opposite of Marx. Curious. Anyway, I like to think the cataloger got his or her hands slapped here!)