Quote:
Then you'll need a specialist (Clive?)
Perhaps individual panes were guillotined from the sheet
Unfortunately, I am very far from a specialist

The 1878 Transvaal Queen Victoria stamps were printed in sheets with the outer edges left imperforate.
As a result, the four corner stamps in a sheet were imperforate on two adjacent edges. The stamps from the left side of the sheet would be imperforate on the lefthand edge, similarly, the stamps on the right side of the sheet would be imperforate on the righthand edge. And the remainder of the stamps would be perforated all around.
It is interesting to note, that despite being scarcer, for example, only four stamps per sheet are imperforate on two sides, SG lists these stamps with one or two edges imperforate at about a 30% discount from the fully perforated examples.
Clive