PCGS 2006-P Colorado quarter with the reverse clad layer missing. The coin is copper on its reverse, because the clad layer was missing before the coin was struck. Missing clad layers are most desirable on the "state side" of state quarters, since that is the most interesting side of the coin. Scarce state for missing clad layers. MS62 Red/Brown
NGC 2005-P Minnesota quarter reverse missing clad layer. The coin is copper on the reverse side, because the clad layer was missing before strike.
MS64 Red/Brown
NGC 2002-P Louisiana quarter reverse missing clad layer. The coin is copper on the state side, which is the most desirable side to have missing.
A scarce state for missing clad layers...