The first Sarawak stamps was officially issued to the public on March 1st, 1869. Of Three Cents denomination, it bore a portrait bust of the first Rajah Sir James Brooke, despite the fact that he had died some nine month earlier. Although the reasons which prompted the Government of Sarawak to order a stamp are not know, it is probable that it was intended to serve both postal and fiscal purposes.

The Messrs. Maclure, Macdonald & Macgregor Issue of 1875
The postal rates that had been the subject of the 1874 agreement between the Governments of Sarawak and t

The order was placed with the same printers who had been responsible for the two previous stamps, Messrs. Maclure, Macdonald & Macgregor of 37, Walbrook,E.C. & Glasgow and the design remained virtually the same as the 3 cents stamp of 1871, only the value being altered. Although the actual date of issue is not known for certain it is reasonable to assume that the five stamps became available to the public on January 1st, 1875 as planned.
The De La Rue Issues of 1888 to 1897
The government of Sarawak decided to place an order for a completely new series of stamps from Messrs. De La Rue & Co. Ltd. The denominations required the same as those already existing, namely 2 cents, 3 cents, 6 cents, 8 cents and 12 cents together with an additional value, 25 cents. The first supplies of this new series reached the country and were placed on sale on November 10th, 1888.
The De La Rue Issues of 1888 to 1897

The De La Rue Issues of 1888 to 1908

Stamp Issue 1889 - 1891

Stamp Issue 1892

February 1895
The Perkins Bacon Definitive Issue of 1895

Stamp Issue 1899

The De La Rue Issues of 1918 to 1923

The De La Rue Issues of 1928 to 1929

1st May 1934
The Bradbury Wilkinson Issues of 1934 & 1941


1st June 1946
The Sarawak Centenary Commemorative Issue of 1946

16th April 1947
The Royal Cypher Issue of 1947

1st January 1950
George VI definitives issued




1st June 1955
First Queen Elizabeth definitives issued





Source
More detailed information on the postal history of Sarawak is contained in Edward Proud's book "The Postal History of British Borneo"
http://britborneostamps.org.uk/
http://sarawakstamps.com/