Classic Prime Mold Variation? WTF

I am currently ont he hunt for the (seemingly rare in my area) Classics OP, since my first one has become teh broken (
). Looking at them in the box in the stores, I noticed something rather...odd. Just below the left window on the edge, there is a tiny rectangular nick that is not on the other side and wasn't on the one I had that broke. Note that this is on lots of them I have looked at.
So I ask: WTF? Is this some mold variation that I have never heard of?

So I ask: WTF? Is this some mold variation that I have never heard of?