There isn't much information documented on Palestine Mandate coils, and from what little there is - in broad strokes - coil stamps existed in one of two forms: one was by paste-up from guillotined strips and the other was by continuous coil.
The paste-up types don't exhibit any special perforations, they look like regular postage stamps. But the continuous roll types have - every few stamps - one with either a very thick (wide) tooth or one with a very narrow tooth:
This is a 5m strip with a "key stamp" bearing the thick tooth:
This is a 10m strip with a "key stamp" bearing the thin tooth (barely perceptible in the image):
My question is, why would continuous rolls have these types of perforation and what purpose did they serve? Is this phenomenon observed on coil stamps of other countries?