The Tone Amplifier seems to be something like the bacon donut ring upside down, but bigger. I have an early Arthur E Smith banjo that has a donut on steroids as tone ring.
Has anyone heard a banjo with a Tone Amplifier? The reference to the back row suggests that volume is being amplified as well as tone. Distantly related to this is the name Paramount gave to their resonator. It was the Acousticon.