The Columbia 15000-D Series Discography (1924 - 1933)Columbia's 15000 D series was the record industry's first acknowledgement of the commerciality of American rural music. This comprehensive discography documents all 783 78 rpm records in the series, recorded between 1924 and 1933, including a numerical listing, session locations, recording dates, matrix and take numbers, label copy, and sales data. Plus: special sections on the 20 best selling records in the series, a listing of all known Royal Blue