ARC was acquired in 1938 by the Columbia Broadcasting System (CBS, which, in turn, had been formed by the Columbia Phonograph Company, but then sold off). ARC was renamed Columbia Recording Corporation. The Columbia Phonograph Company had international subsidiaries and affiliates such as the Columbia Graphophone Company in the United Kingdom, but they were sold off prior to CBS acquiring American Columbia. RCA Victor Records executive Ted Wallerstein convinced CBS head William S. Paley to buy ARC and Paley made Wallerstein head of the newly acquired record company. The renamed company made Columbia its flagship label with Okeh its subsidiary label while deemphasizing ARC's other labels. This allowed ARC's leased labels Brunswick Records and Vocalion Records to revert to former owner Warner Bros. which sold the labels to Decca Records. Columbia kept the Brunswick catalogue recorded from December 1931 onward which was reissued on the Columbia label as well as the Vocalion label material from the same time period which was reissued on the Okeh label. Wallerstein, who was promoted at the end of 1947 from president to chairman of the record company, restored Columbia's status as a leading record company and spearheaded the successful introduction of the long playing (LP) record before he retired as Columbia's chairman in 1951. James Conkling then became head of Columbia Records. Also in 1951, Columbia severed its ties with the EMI-owned record label of the same name and began a UK distribution deal with Philips Records, whereas Okeh Records continued to be distributed by EMI on the Columbia label.
ARC kept the Brunswick catalogue recorded from what date?