Anyone ever heard of this in reference to a JCM 800?
Marshall JCM 800 2203
Peavey 5150 II
Marshall 1960AV
Avatar 4x10
Gibson Studio Alpine White
DL4 Delay Pedal
Boss CH-1 Super Chorus Pedal
Boss TU-2 Tuner Pedal
Boss NS-2 Noise Suppressor Pedal
Holy Grail Plus
Ernie Ball Volume Pedal Jr.
Maybe you're talking about the kerry king model?

"The Beast switch, that activates custom noise gate and variable gain boost with King's custom EG curve!"