OK. That's what happens when the planchet slips a little bit when it's struck between the dies. These dies were deteriorating. We could discern that by the striations in the fields. That makes these planchets all the more susceptible to doubling because the surfaces of the fields are uneven, bumpier. Thus, this is really nothing. It's simply the consequence of bad dies, and a little hop, perhaps, when the planchet was squeezed.
I have this same 1988 D Monticello coin, but gold or copper in color and stamped with 21 over the head. Is this something or did someone before me just deface the coin?
Howdy John. You may not be aware, but you are asking your question in a 5 year old thread. If you start a new thread with pics of your coin you will probably get some responses. Please include full pics of obverse and reverse of the coin and you will likely get some responses.