Chronological arrangement is common in collections of historical materials in which the sequence of historical events takes precedence over name access. It is also commonly found in business correspondence or fan mail in personal papers.
The original order of the material should be respected when considering alphabetical versus chronological arrangement. In many cases it is sensible to maintain an existing chronological arrangement, but this strategy should be weighed against the potential demand for name access, and security concerns if there are high-profile autographs in the collection. Effective name access often can be achieved through description, even when the chronological sequence is preserved.
Undated letters in a chronologically-arranged series or sub-series may be filed at the end of the sequence.