unused Block Larger Than four 50c Parcel Post (Q10), bottom imprint and plate no. 6427 block of six, fresh and intact, large 20mm selvage, bottom three stamps never hinged, left pair has light natural gum bend, top center stamp has small faint thin, centered to left, perfs. clear to just touching on two stamps, otherwise fine appearance, an extraordinary rarity in a proper configuration plate no. block of six, one of very few recorded, Scott retail $13,500.00 photo est.