Ultimately, the New Orthophonic curve was disclosed in a publication by R.C. Moyer of RCA Victor in 1953. He traced RCA Victor characteristics back to the Western Electric "rubber line" recorder in <answer>1925</answer> up to the early 1950s laying claim to long-held recording practices and reasons for major changes in the intervening years. The RCA Victor New Orthophonic curve was within the tolerances for the NAB/NARTB, Columbia LP, and AES curves. It eventually became the technical predecessor to the RIAA curve.
How far back could these recording practices be traced?
1925