Most of the "Pre-BIE" die breaks and chips I've found "go nowhere", in other words they don't eventually become a major/full BIE. But in my latest search of some 55-S BU rolls, I was lucky enough to find a Pre-BIE that is a precursor to Cohen B906, Cuds On Coins LDB4-1955S-006B 4DH+. If you are familiar with the 1955-S BIEs, this is the one that fills the upper half of the space between B and E.
I'll start by showing B906, followed by the new discovery coin, which Cohen might have called BA905, so that's what I will call it.
B906
And here is BA905
And here is an animation I made flipping back and forth between the two
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