In my early years doing research at the Family History Library in Salt Lake City, Utah, these records were still available in paper format in large binders on the shelves of the Library. This research service ended in 1966. Eventually, the sheets were all microfilmed and made available on 4018 rolls of microfilm.
The files are described by the FamilySearch Catalog as follows:
Consists of genealogical research notes, family group records and pedigree charts, and correspondence between the Research Department and the person sponsoring the research.
Access to the files is provide by the indexes listed below under the heading "Major Indexes to Research Department Patron Files." Following the indexes, description of several other indexes are includes. These other indexes were compiled for internal control purposes and do not provide access to the files. However, they may occasionally provide information of value to researchers.
-- CARD INDEX TO PATRON'S PEDIGREE SURNAMES -- Includes name of locality where patron's ancestor resided, surname of ancestor, period of years in which the ancestral family was known to have lived in the locality, and the name of the patron having the research done. Index incomplete; includes four counties only.
-- INSTRUCTIONS -- Located desired ancestral surname in the portion of the index covering the ancestor's place of residence. Then find the microfilm numbers for those patrons' research files by using the Card Index to Microfilm Patron Files.This vast collection has yet to be digitized and must still be accessed in the Family History Library in Salt Lake City, Utah. You can find the complete list of the microfilms in the FamilySearch Catalog on FamilySearch.org.