A rather unusual Sandakan postmark without the outer circle. I make the date as 5 OCT 1924. Some Sandakan date stamps, in particular D3 and D13, can become worn and the circle appears as a series of dots rather than completely disappeared. This date stamp looks more similar to D24.
1c stamp with dotted circle postmark dated APR 1900 probably D6. It has part of a "D" in blue at the lower margin possibly the end bit of "registered".
Dotted postmarks D4 and D5.