What do you mean by a "Wexler #4"? Interesting find. Does the coin you posted really have a Lamination or is it just a Plating Blister do to the fact that it is a copper plated Zinc Coin? It looks to me like a blister that has expanded to the point where it has ripped open and is now leaking out zinc oxide between the the "E" & "C" .
Wexler DDO-004 too . http://doubleddie.com/828781.html I'll take a new image between the E & C where the rip, or tare is .
Improper Alloy Mix can result in a "Woody". A poorly mixed Alloy may contribute to a lamination peel. A lamination error is caused by a folding of metal upon itself. They are listed as two separate categories. http://www.error-ref.com/part-v-planchet-errors/
In the case of the Copper Plated Zinc (CPZ) cent. The Core is Zinc, not an alloy of two/three different metal that are mix together. There is no Improper Alloy Mix that could cause a Lamination Error in/on a CPZ cent.
Lamination errors can also result from trapped gas bubbles in the melt, so single metal, non-alloyed coins CAN have laminations as well. Molten metal often has dissolved gases in it, so once the melt is liquid it is kept that way for a little while to allow the gases to come out of solution. Also if the melt temperature is too high you can have some volitaization of the metal that creates bubbled (as when water boils) This is less of a problem today than it used to be because they have better temperature control, and the inductions furnaces set up convection cells in the melt which help to release dissolve gases. But it IS possible for the zinc core to have a lamination
It could if there foreign material, a piece of carbon, a little slag etc. If it is imbedded in the ingot it doesn't roll out like the metal does. Think of it like pie or pastry crust. A properly made crust had little bits of butter all through it. When it gets rolled out the bits of butter get spread out as well but it keeps the dough above and below from bonding together and the result is a flaky crust. Ingot with an inclusion gets rolled out and you get a "flaky" planchet.
That one confuses me. I could see if a gas bubble near the surface was trapped and when struck, built up pressure that was released when the die lifted causing the “blowout”. As @Conder101 pointed out, gas bubbles can be retained in a melt. However, if the original ingot had a bubble, I would expect it to be flattened and elongated during the strip rolling process, not stay as a spherical bubble. Therefore, I don’t see how this could be a mint error. Can anybody tell me what I’m missing?
Thanks for the reference. I learned something new. I don’t think the defect on the coin you posted is due to tensile stresses. Error-ref says the tearing is due to the metal being brittle and “breaking” instead of deforming. Your coin looks like there the metal was malleable and deformed, not brittle. Just my thoughts
The raised rim of metal in the field area at the left edge of the "hole" tells me it was the result of PSD.