Many of the letters currently held in the collection are copies from originals, but as the records have been so well-kept in the 20th century, their authenticity is not in question. The time period of the correspondence is 1922 to 1945.
Among the letters preserved in the archive, many are duplicates of original documents; nonetheless, due to diligent record-keeping throughout the 20th century, their authenticity is not contested. The communication dates span from 1922 to 1945.