1942 Nickel With No Reverse, Very Odd

Agree, doe look like a split planchet! Wher'ed you find it?

This is a Split Planchet. Congratulations on the find! Where did you find this? Welcome to CCF!

Planchet split after striking. No sure why you should have it slabbed. It is obvious what it is, and is the grade really that important? All the value is in the error.

That is a neat find. Over the past 50 years I have found three of them.....one Buffalo nickel, one silver War Nickel and one regular Jefferson nickel. All of mine are from the 1930's and 40's.

I believe it is due to improper annealing.

Agree , Split planchet after strike.
Here is a pic of a 1960-D cent that split before strike and a 1924 Buffalo nickel that split after strike. They are both oriented so the internal striations of the metal are shown moving in the same direction

Actually goes back the melting and and mixing of the metals in the melt. There were bubbles in the melt and in the ingot cast from it. When the ingot is rolled the bubble trapped inside gets spread out but the metal above and below the bubble are not joined together. If the bubble is large enough, about the diameter of the coin r larger, and the blank is punched from the strip where the bubble is, the planchet can split like this.

Sometimes if the second piece is smaller, it maybe struck onto another coin and fall off again. It just unknown what happened?

Here is an example of a coin stuck through on a foreign object. (smaller planchet)

Here is one of the second planchets that fell off after the strike. (no from the same coin as above: