So I think you are trying to say that there might be a more valuable painting underneath the one you can see, like an undiscovered Edvard Munch. You might want to contact a University near you that has an art conservation department. They might be able to you give you a better idea of what is underneath and might want to use it for a student project.
As an aside, forgers would look for older canvases to fit the time period of those they wanted to copy.