I've done some research on this die variety, and published a cross-reference between CONECA (RPM), Cohen (BIE), and
Cuds on Coins (BIE) listings. It's a very interesting die, showing up in no fewer than 12 RPM stages on CONECA, 7 BIE stages in Cohen, and 4 (so far) BIE stages on
Cuds on Coins. Here is a link to what I've published:
http://goccf.com/t/433914
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http://macrocoins.com