When airmail postage rates increased from 6d to 7d there was no stamp in
the 1960 Definitives issue to cover this rate - the 7d Definitive not being
issued until 1966. To fill the gap, the
1931 Arms Postal Fiscals die was
used with no value printed in the panels at the top and bottom, but with 7d
overprinted in black. The
1965 Sir Winston
Churchill - Commonwealth Day commemorative also helped span the gap
until 1966.
The bulk of used stamps left the country and so this
stamp is rarer used than mint.