Got this coin back the other day. I've had it in my collection for around 25 years and finally decided to verify what I believed it to be and it came back what I thought it was. After years of people telling me it was heat damage I feel a little vindicated that it was a gas inclusion. I just wonder how this would get out for circulation to begin with. The only thing I can figure is that because it was a defective planchet it was kicked out of the stamping process but then at some point someone just pilled it in with the finished product.
It is the unstruck luster of the planchet, it is graded on the planchets surfaces, the more incomplete, less the grade.
