Retired by the Air Force and accessioned by NARA in 1983, the Central Decimal Correspondence Files, also referred to as the Sarah Clark Collection (NC3-342-83-1, 1175 cu ft), and the R & D Project Case Files (NC3-342-83-2, 3155 cu ft) both are labeled R & D Project Files, and there is some overlap (and confusion) between the two. The Sarah Clark Collection is the Central Decimal Correspondence File for the Air Service/Air Corps/Army Air Force/U.S. Air Force Material and Research and Development Organizations from WW I to the Korean War.  The Air Force formally designated these records the “Sarah Clark Collection”  on April 20, 1960 to honor the 39 year career of Miss Sarah Clark, the head of the Central Files unit who was moist responsible for their arrangement, maintenance, and retention. The Sarah Clark Collection has records dating as early as 1916 thru 1949.  They are arranged by “RD” numbers arbitrarily issued when the records were retired and consecutive box numbers, both of which are needed to identify individual boxes in the stacks. . There are also copies of the folder lists made of the records by the Air Force before they were retired. There is microfiche finding aid to this collection that is exceedingly difficult to use.