Rudolph introduced his continuous indexer in 1893 at the meeting of the American Library Association at the World's Columbian Exposition in Chicago. The Rudolph Continuous Indexer was marketed as a less costly alternative to the card catalog. Competition from Melvil Dewey's Library Bureau and its card catalog products was too great, however, and the Rudolph Continuous Indexer was short lived. The major drawback to Rudolph's indexer was that only one person could use it at a time.
It is wonderful that the Newberry Library has preserved an example, perhaps the only example of a Rudolph Continuous Indexer. The photograph above was taken by Richard Douglas. For more on the Rudolph Continuous indexer click here.