Railway Travelling Post Office for mail between Jesselton/Kota Kinabalu and Tenom with drop points along the way. TPO1 was in use between 1963 and 1979.This is a CTO cover which despite the name and address, never went through the normal postal process. Moreover, the rate for a light letter to GB was 35c from 1957.
Correction: 20c was in fact the correct rate for surface mail rate in 1965 but I would still maintain these 2 TPO covers were both CTO due to the lack of other markings etc.
TPO2 was used from 1964 to 1977. There is obviously an overlap with TPO1 and TPO2. They were used on the same route. I am not sure why they have different numbers.
Kudat MTO6 was a mobile PO. I do not have a date for this one. Attractive envelope with different cachets. The cover left Kudat, transited at Kota Kinabalu and arrived at Tawau 2 days later.Update The MTO6 is probably due to an error in the printing of the labels as the letters P and T sound so familiar to the uninitiated. It should have been MPO6 which was the designated MPO for Kudat.
Kota Kinabalu PPB1 was a mobile PO that was used in the 1970s. PPB stands for Pejabat Pos Bergerak in Berhasa Malaysia which translates to Mobile Post Office.
The Mobile PO postmarks and registrations cachets of NB/Sabah provides a potentially rich area for detailed study. There are 33 different town postmarks and 40 registration cachets listed in the Sarawak journal from 1963. I would imagine there would be some more which are yet to be discovered.