Brunei Stamps during Japanese Occupation
When the Japanese invaded Brunei in 1942, they occupied the entire country. They still need a postal service. Being practical, they went to the Post Office and discovered that the British conveniently a large number of unused stamps. All the Japanese had to do was to overprint the stamps with the words Japanese Imperial Government.
I thought I had the entire set, and it was only lately that I discovered I had a missing 1 cent stamp which I had since tracked down and obtained. The above is the entire set that was used by the Japanese. There is another 3 cents stamp (which I would love to get my hands on) which was later overprinted and that for the time being became the most expensive Brunei stamp valuing at about $20,000.
The 8 cents and 15 cents stamps were not used during the British rule. They were procured early but unused until the Japanese came. So these two stamps were only used between 1942 to 1945.