In 1954 Schellenberg was awarded a Fulbright lectureship in Australia and New Zealand where he made landmark changes to Australia’s national archives program. The result was a series of pamphlets which became the groundwork for his first major book publication, The Appraisal of Modern Public Records (1956). This work was an attempt to supersede the Manual of Archival Administration by his older contemporary Sir Hilary Jenkinson. Schellenberg referred to Jenkinson as an “old fossil” whose outdated ideas were in need of revision. Schellenberg, in stark contrast to Jenkinson, believed that a record’s “character” rather than its “quality” should be the basis for evidentiary appraisal decisions. Character, as Schellenberg described it, could be categorized as one of two types: those records possessing primary value and those with secondary value. Schellenberg distinguished primary value as one which reflects the “administrative, fiscal, legal, [or] operating” actions of the record creator. Those of secondary value, he argued, should be kept because they exhibit a an unintended new use which emerges after the record becomes inactive. He further divided secondary value into two types: evidential value and informational value. Evidential value reveals “evidence” as to the "structure, functions, and hierarchical interrelationships of the creating body,” while informational value, means the record contains a unique concentration of information about “persons, corporate bodies, things, problems, [or] conditions.” Active selection of records by the archivist, based on these values, Schellenberg argued, is a better way to reflect the character of an organization and to preserve its history than to passively collect everything. 
Following this publication, Schellenberg work was translated into several languages. The success of his book let to his appointment to Assistant Archivist of the United States, a post he held until 1963, after which he taught university courses in archival administration and document preservation. Schellenberg’s second major work, The Management of Archives (1965), emerged as a product of his teaching experiences. In it he applied archival principles to the disposal of manuscripts in nongovernmental organizations and controversially suggested that the systematic methods used to teach students in library school lend themselves to teaching archival theory better than those of history programs.
T. R. Schellenberg died on January 14, 1970 at the age of 67 in Arlington Virginia. While his two major works remain classics in the history of archival administration, and fundamental to the understanding of the profession, archivist-critics of the post-custodial era have specifically targeted Schellenberg’s appraisal theory and methods for revision, particularly Terry Cook, Leonard Rapport, Frank Boles, Luciana Duranti, Hans Booms, Charles M. Dollar, and Terry Eastwood.