Dear Ms. Ink,
Thank you for posting your request on History Hub!
We searched the National Archives Catalog and located the Issuances, 1962 - 1973 in the Records of the U.S. Forces in Southeast Asia (Record Group 472) that may include records, such as Army Regulation AR 25-50 “Preparing and Managing Correspondence,” regarding official abbreviations for military ranks in use during the Vietnam War. For more information about these records, please contact the National Archives at College Park - Textual Reference (RDT2) at firstname.lastname@example.org.
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.
In addition, we suggest consulting the websites of the Defense Technical Information Center, the Army Publishing Directorate, and the U.S. Army Center of Military History. These websites have many digitized versions of primary and secondary sources available online that may include information relevant to your request. You also may find it useful to consult the Department of Veterans Affairs’ handout Military Ranks, Department of Defense’s website US Military Rank Insignia, and Department of the Army’s Rank Insignia of the U.S. Armed Forces for information regarding current official abbreviations for U.S. military ranks.
We hope this is helpful. Best of luck with your research!