I have somehow manage to accumulate a small selection of this uncommon parcel post cancellation. It is quite attractive as it is usually in deep blue or violet. My PP5s are not good enough for showing. I am waiting for my PP6 which I believe to be one of the rarest of Jesselton cancellations. These cancellations were used on parcels which were normally subjected to a lot of trauma and were unlikely to survive intact.
The recorded dates of use for Jesselton PP3 was between February 1918 and October 1923 according to Proud. But one can clearly see dates of 1927 and 1929 in the above stamps. So there was some overlap with PP5 (where was PP4?).