Norman,
I believe you are correct the Rabco was the first accessory (separate component) tangental arm. But by the late '70s several Japanese companies offered tables with tangental arms. I had one of the Pioneer units (picked up in Japan by a Navy buddy) which was nearly the same as the Phase Linear version sold in the US.
Bruce Thigpen worked for Maplenoll, designing their air-bearing tangental arm prior to starting his own company, Eminent Technology, in 1982. The first ET product was an improved version of that arm. During the '80s Souther and other companies also introduced tangental tracking arms.
Back to the AR, VTF was not the only adjustment with that arm. There is a set-screw on the underside to adjust arm length for stylus overhang. However offset is fixed because headshell slots are not provided.
I believe you are correct the Rabco was the first accessory (separate component) tangental arm. But by the late '70s several Japanese companies offered tables with tangental arms. I had one of the Pioneer units (picked up in Japan by a Navy buddy) which was nearly the same as the Phase Linear version sold in the US.
Bruce Thigpen worked for Maplenoll, designing their air-bearing tangental arm prior to starting his own company, Eminent Technology, in 1982. The first ET product was an improved version of that arm. During the '80s Souther and other companies also introduced tangental tracking arms.
Back to the AR, VTF was not the only adjustment with that arm. There is a set-screw on the underside to adjust arm length for stylus overhang. However offset is fixed because headshell slots are not provided.