Art Davis worked for Cinema Engineering, which was marketing a form of this kind of attenuator in
1953 and probably earlier.
(I provided the scans, from old magazines)
As we know, slide-faders became the preferred interface for analog mixing boards, eventually
replacing rotary faders in almost all applications (although small-format mixers sold by companies
like Behringer, Mackie, Alesis and others still use rotary faders). There have been many varients on
slide-faders over the years. In the 60's, Fairchild sold a fader that controlled the intensity of a
light source, which then interacted with a LDR to control gain, branded "Autoten." In the 70's,
Audio Designs & Manufacturing (ADM) patented a mechanical system that drove a pot that controlled a
VCA to control gain. The advantage of the ADM "Slidex" attenuator was that liquid (perhaps coffee at
a TV station, beer at a radio station or something more exotic at a recording studio) could spill
across the slider section of the console and not short out anything, within reason.
Here is the Slidex patent:
-- Tom Fine