This was actually the last occasion for some time where there could be said to be a distinct new ‘set’ of definitive stamps. The high inflation of the 1970s and increasing postal costs led to regular tariff changes, and as the years went by, Machin values were added or dropped on a rolling basis to reflect the current rates. Of this set, the first to be withdrawn was the 3½p in 1975, followed by the 1½p, 2½p, 3p and 4p in 1977 and the 6p and 7½p in 1979, with the colour of the 9p changed in 1976. Several were later reintroduced in different colours when needed as makeup values – only the 1p and 2p were constants throughout the life of the Machins.
While this process had certainly happened with earlier definitives, it usually affected only a few stamps. For example, the Wildings saw the 11d value dropped and a 4½d added, but the rest of the values remained the same throughout – and so on cover (where the various watermarks are hard
