2d pale blue (plate 1) strip of 3, each with full margins and tied to a legal letter from Liverpool to Manchester which would have contained a mortgage deed hence the 6d rate. Letter dated May 21st 1840 and on the reverse top flap a very fine Liverpool cds for May 22nd 1840 in the same orange shade as the Liverpool MXs. This item is recorded in Jackson's book of May Dates where it is described as a 'divided strip of three'.
As seen in the images the stamps have been partially divided vertically but not separated. Such a method was used in the post offices at the time by the postal clerks to speed up the separation when the stamps were needed.
Jackson records only 70 examples of the 2d blue used in May 1840 on covers and pieces including combinations on Mulreadies. This compares with 86 examples of the 1d black on the first day of issue, May 6th 1840. 24 examples have faults to the stamp(s) and/or are not 4-margined. Only 1 other 6d rate is recorded between May 6th and May 21st and with that example the 2d blues are touched and or torn/damaged.
May Dates page 151.