Dear Ms. Allen,
Thank you for posting your request on History Hub!
We searched the National Archives Catalog and located Central Decimal Files, 1910 - 1963 and Subject-Numeric Files, 2/1/1963 - 1973 in the General Records of the Department of State (Record Group 59) that are the primary record series for Department of State cables from this time period. Also, records of specific embassies and consulates are in Records of the Foreign Service Posts of the Department of State (Record Group 84). See Filing Manuals - State Department for assistance using these records. The National Archives also has custody of appointment cards and Department of State biographical registers that may be used to determine Mr. Allen's assignments. For more information about these records, please contact the National Archives at College Park - Textual Reference (RDT2) via email at Archives2reference@nara.gov.
Due to the COVID-19 pandemic and pursuant to guidance received from the Office of Management and Budget (OMB), NARA has adjusted its normal operations to balance the need of completing its mission-critical work while also adhering to the recommended social distancing for the safety of NARA staff. As a result of this re-prioritization of activities, you may experience a delay in receiving an initial acknowledgement as well as a substantive response to your reference request from RDT2. We apologize for this inconvenience and appreciate your understanding and patience.
Some Department of State biographical registers have been digitized and are available online through resources such as Google Books and the HathiTrust Digital Library. We located a 1963 edition of the Biographic Register that lists his assignments to that date on page 6. He may have had additional assignments in later years.
You also may wish to search the website of the Department of State’s Office of the Historian for results from the Foreign Relations of the United States (FRUS) and other resources on the website. We searched for the exact phrase “Francis O. Allen” and located 7 results. The citations for the documents in FRUS may be used to locate the original documents in NARA custody.
We hope this is helpful. Best of luck with your research!