I have a 1964 Jefferson that, when I touched it, it felt strange. Both sides are raised higher around the edges and has a abnormal lip to it. I also did a side-by-side comparison with a normal nickel and the 64 is shorter in diameter but taller in height. Also, the side looks like it has some weird double plating or something, I don't know. I don't know much about these things but was hoping someone could help me out with any info. I will upload pictures but cannot guarantee the quality. thanks