British Military Administration (BMA)
Very few postmarks were used during BMA and mainly from the two main towns - Brunei and Kuala Belait. I'm not sure about postal services in Tutong and Temburong during BMA, but both Muara and Seria were not opened until 1948 and 1951 respectively.
Two varieties of postmarks were produced: (a) A three-line postmark provided by the Straits Times in Singapore; and (b) An Australian pattern cds. Both varieties were available for both towns. Two further varieties found for the three-line postmarks for both Brunei and Kuala Belait.