1999-P State Quarter. Pennsylvania--Struck on an Experimental Planchet--MS-67 (NGC).Intensely lustrous olive-gold surfaces are fully struck with a silky smooth appearance. Although the Sacagawea dollar was first issued in early 2000, the manganese alloy in its planchets was developed during 1999 and tested using State quarter dies, which were similar in diameter. For each of the five 1999-dated State quarter types, a small number of examples were struck at the Philadelphia Mint in a green-gold manganese alloy, as here. These pieces are technically patterns, but they are not listed in the 10th edition of the Judd reference and are even listed as "Mint Errors" by at least one of the major certification services.