This coin was struck from the dies used to strike regular Proof 1866 Quarter
PCGS has certified 2 Copper
1866 Quarter Dollar Die Trials, the finest of which are a single PR-63 and a
single PR-62 CA.
Sources and/or recommended
"United States Pattern, Experimental and Trial Pieces" by J.
Hewitt Judd, M.D.
PCGS Population Report, July 2005, Professional Coin Grading