The 1d black (from plates 1a and 2) went on sale in British Post Offices on 1 May 1840 and became valid for postage on 6 May 1840. It was replaced by the 1d red in February 1841 but remained on sale until stocks became exhausted.
A total of 11 printing plates were used during these ten months, although plate 1 quickly showed signs of excessive wear and was extensively repaired. These two states of plate 1 are referred to as plate 1a (the original state), and plate 1b (the repaired state).
Several of the “black” plates (1b, 2, 5, 8, 9, 10 and 11) were also used to print 1d red stamps and such stamps are included on these pages rather than being shown with the remainder of the 1d red stamps.
Although superseded by later issues, these stamps remained valid for postage until all stamps bearing the image of Queen Victoria were finally de-monetized in 1915.