With the introduction of the 1975 Pictorials / Definitives
stamp issue, the Post Office found that the new stamps were too large to
fit in automatic stamp-affixing machines - such as the Postafix machine by
Data Link Co, California.
solved this problem, but as an interim solution, supplies
of the 1970 Definitives /
3 cent and 4 cent moth stamps were overprinted by the
Government Printing Office with 7 cent and 8 cent denominations and made up
into rolls of 400 stamps.
Some very crude forgeries of the 7 cent
overprint were discovered by stamp collectors shortly after this issue was
released - the intention apparently being to defraud the New Zealand Post
Office of four cents revenue rather than fool collectors. They can be
easily identified as the '7' surcharge is considerably smaller than
on the valid stamp and the ink is dull compared to the gloss of the Post