You want a serious answer, I'd say they had something to do with the cars radio system. Probably an ancient "amplifier" of some sort (although I'm probably wrong as that would be the easy answer)? In any case, the fact that you found them "laying around in your garage", covered in dust tells me that they were probably removed years ago as they were of no use.....like most factory radio components. Hence the "junk" term.
its part of the reverb set up for a deluxe radio
edit . they are actualy kind of cool sounding they give kind of a echo effect
somewhat like plucking the strings of a guitar
that is cool i had a black 66 GT coupe that belonged to a ford rep. he drove from Santa Maria to mexico the car even had a ford rep dso. it was fully loaded ,air,console,remote trunk release,trunk rack,rally pack ,red poney interior,cruise controll,and the radio set up. its in a museum last i heard
Not sure if its the same as studio sonic, all i know is its called Vibrasonic and was optional on a lot of the 60's cars.I never got a chance to hear how it sounds because when I "aquired" the car when i was 16, i just pulled everything out,didnt know things would become collectable.