cover Usage, 1901 (March) envelope registered from London to Saltsburg (Pa.) bearing ½d. blue-green (uncancelled), 1/- green and carmine and 1881 1d. lilac pair and strip of five (affixed over edge of cover), showing purple framed "SUPPOSED LIABLE TO/UNITED (2) STATES/CUSTOMS DUTIES"; blue crayon strokes cross three 1d. lilacs, otherwise fine