I have a 1974 quarter that is most definitely clad in something because the inner layer is wearing away very clearly all the way around the coin. I’m very interested to find out what this is. I also have a 1979 quarter that is clearly sandwiched together into three very obvious layers.
I don't understand what you are trying to convey. Clad quarters are 3 layers. 2 outer layers made of Cupronickel and a middle copper core. Billions of clad coins are made the same exact way. The first quarter you described sounds like erosion to the middle layer of copper. That occurs when the clad quarter sits in a corrosive liquid. You need pictures!