This reminded me that I don't know anything about it so I'll do some searching right after I make this post.
About 45 years ago when I was a little kid in Philadelphia, I was digging at the playground and found a commemorative medal that was issued by the First Centennial Congress during the Centenial Exposition in Philadelphia in 1876. It looks like a huge penny (about 3" dia X 3/8" thk ...errr aahhh ~7.6cm d. X ~1cm t.) very ornately engraved with relief sculpture work, in very small letters in one area it has the name of somebody from South Carolina if I recall correctly. I just put it into my steel coin collection box. Everytime all the kids looked at it we said things like "...it's probably worth millions to a collector so let's sell it and get rich..." I still have it so maybe that's one reason I'm still not "rich".
My edit after searching: after all these years the mystery penny is being identified:
