1968 D LMC Planchet Error?

PMD maybe? Not sure...

I will confirm - that's an incomplete clip. Extremely cool find! It occurs when the blanking die doesn't completely cut the blank out from the coin strip. When the strip doesn't move forward enough, the blanking die can punch another blank out over its previous markings, creating a blank with the circular punch mark that you see on this coin.

I'd normally be concerned that the punch marks don't go through the design rim, but everything else is as one would expect from this error. Incomplete punches are probably most common on cents, specifically those from the 1967-1973 time period. If the weakness that I see is from strike/poor die quality and not wear, I'd estimate that its a $90+ coin.

Here's a dancing fruit for ya:

The idea of the edges of the clip surviving so clearly through the pressure of the strike, right across the devices, is kinda difficult intellectually but the other evidence fits the theory. Radius looks right, it's way too heavy for counting machine marks. I could see the strike slamming metal against the collar as reason for the crack to fuse there, but that argues against the crack surviving clearly elsewhere.

So I'm in learning mode.