Yes; it certainly looks a bit home-made.
At first I was wondering if the P.B. is something to do with "Post Block" (as in the technique of Post-Block Correction); but I suspect that what we are looking at is simply an oscillator that produces masking sound "on demand".
Although I notice that Rick Maybury mentions that the circuit looks like it delivers a "high voltage" to that connector. Otherwise, what can that neon be for? Simply for driving the headphones, would be my guess.
If I had the time I would have liked to have sketched out that circuit!
By the way, some of those caps look a fair bit younger than the Germanium transistors.
Anyway, take a look at
this* abstract.
... stammerers often improved in presence of background noise.
But Rick Maybury's website is brilliant. Thanks for pointing it out.
*
Cherry & Sayers
