1960 D Lincoln Broken Die Piece Struck On Reverse?

Very nice struck through!

Well if it were a fragment it would look like this:

But it appears the fragment landed upside down on this coin. But what concerns me on this one is the full strike on the OP's coin with the area showing it altered on the coin? Possible dropped letters? We might need Mike Diamond on this one?

Sent message to Mike.

This coin was struck through a very thin, previously-struck fragment of metal. A thin piece of metal, such as a delaminated flake derived from a planchet, landed beneath the planchet that preceded the planchet represented by this coin. The flake was struck against this planchet where you find the motto E PLURIBUS UNUM and the flake molded itself to the corresponding recesses of the reverse die. The overlying planchet was then ejected and the struck flake moved to a different part of the striking chamber. A fresh planchet (this coin) came to rest on top of the struck flake, and the two were struck together. The result is a set of correctly-facing, incuse letters. The other possibility is that this cent was struck through a large, multi-element dropped filling. But the sharply defined borders and the lack of any other grease-struck areas makes this less likely

I suppose the next question is how common is this? Shall it go in my rarities folder or my common mint error folder

Understandably this depends on the demand for such errors but would anyone know a general value of an error like this?

Very cool coin. Thanks for sharing.