Any folder, and therefore all the correspondence, can be secured at once. Only an instant's consultation of the card index is needed and not even this will be necessary after the system has been in use for a short time, for the clerk soon memorizes the numbers. The latest letters are always on top.
Numbers cannot be confused. Blurred copies are easily identified. Only transient correspondence - one or two letters from the same source - are arranged alphabetically. In some offices where only a very few letters are ever received from any one firm the entire arrangement is alphabetical.
In the same amount of space double the number of letters can be filed. Old and useless matter is removed and new takes its place. There is no waste space on account of drawers filling irregularly, as one has but to shift excess folders and guides from an over-filled drawer to one with empty space.
All correspondence from beginning to end is in one folder. Letters signed by different members or employes of a concern are all filed in the folder with the same number. Cards are made out for each so that the correspondence can be located with any of the names as a guide. Postal cards and small pieces are safe in the folders.
Carbon copies are made, the stenographer noting the number on the letter, putting it on the letter written so it is duplicated on the copy and the incoming and outgoing correspondence are together.
By means of cards in the index, letters and papers may be indexed in so many ways that nothing can be lost. Letters of quotation, for instance, may be indexed both by article and by name. In taking up a subject, as an example, "Repairs on Engine-house," one folder can be devoted to this subject, and all the letters, plans, contracts, etc., pertaining to this work can be filed in one folder, but be indexed by name, subject or in a dozen different ways in the card index.
Capacity for capacity, not only the first cost but the subsequent expense for transfer cases is much less. The index cards may also be used for customers, sales or credit records, and as an index to orders.