Classic "extrusion strike"
- Here's what I informally refer to as an "extrusion strike" or
an "extrusion effect":
In this case it is occuring in association with a partial brockage
and a partial collar.
The coin that produced the brockage interfered with the descent of
the hammer die. Minimum die distance was therefore greater than the
thickness of the coin. However, the intrusive coin produced
excessive localized striking pressure beneath it which caused the
coin metal to squeeze out laterally from beneath the coin and also up
and into the gap between the intrusive coin and the collar. This
rising coin metal actually met the die halfway, producing a
respectable strike on the obverse. There is no strike on the reverse
in this area.
This is one of the few errors (perhaps the only error?) in which you
can have a die-struck surface on one face but no strike on the
Extrusion strikes are associated with indents, partial brockages,
deep and extensive strike-thrus, coins struck through clipped
planchets, and retained cuds. The coin simply needs to be confined by
the collar. The other key ingredient is the presence of a gap into
which the coin metal can extrude.
It's really too bad that this is a state quarter. I'm happy to buy
extrusion strikes in other denominations that are less pricey. If
anybody has any extrusion strikes for sale, I'm all ears. I will be
preparing an article on the topic some time this year.