I found a MS-63 1969S, in my separated coppers which ( I thought) was a true double die. After jumping up and down with glee for a few hours, I finally sent it to PCGS. Once they received it, one of the graders called me and told me it was a machine double not a true double die... worth much, much less than a true double die.

He said this happens a lot. He mailed the penny back to me.