Mulready Envelopes and Letter Sheets were released for public sale on 1st May, 1840, but postal validity was not to be until 6th May, 1840. Any such used before the 6th should have been surcharged and postage collected in cash. Some 42 were posted prior to 'official use'.
This Letter Sheet sent to Malton, Yorkshire was used on the second day. It is a Forme 1, A7 stereo, first row, second position. The sender is unknown as they did not write a message within!