This has to be the least attractive looking cover sent by Oswald Marsh but also at the same time probably the most valuable. This is because of the rare stamp that was used. This 1918 6c+2c olive green has the wider spacing in the surcharge. Only one sheet of a hundred existed for this variety.
A mint example was sold recently for £260. I have not come across a used specimen in an auction and the conclusion is that used items are rare whereas mint examples are seen regularly in major auctions. There should be at a slight premium on this cover which is philatelic. But then this may be the only cover with this stamp. It has a Jesselton cds.
These are my two mint copies together with one with a normal spacing for comparison. Very good fakes do exist so one never knows. But they compare well with my used copy which is most likely to be genuine.
This is a fake used copy with a Kudat cancellation. Only that a 1925 perf 12 stamp with a different shade of colour was used, luckily for us. The fake overprint is very good but the letters look thinner throughout and very important differences include the "O"s being a bit rounder and the "W" slightly wider. But you would need a genuine copy to compare to be certain.