From time to time I see this kind of perforation on Palestine Mandate stamps, that rather than there being round horizontal perforation holes (like the strip on the left), the ones produced look more ovalish (like the strip on the right). Does anyone know why that might be?
The perforation measure on the left strip is somewhere between 13.25 and 13.5, and on the right strip its about 13.5.
I have seen instances of different sized holes along the same axis and for this I've been told it's because the perforation pin has been replaced, and not always by a pin of the same gauge. But here the hole sizes (on the right strip) appear to look consistent.