I'm guessing that it was a limited production of some kind, possibly a reproduction of a unusual prop that was no longer airworthy. I think it will be extremely hard to identify with any degree of confidence.
It may be "airworthy" but not " certificated". The distinction has to do with the conditions of its usage and compliance with FAA regulations and the category of the airplane using it, e.g. "Experimental" vs. "normal".
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