The 1897 issue of stamps were overprinted with "British Protectorate" between 1901 and 1905 for the various values with the $5 and $10 being the last to be overprinted. Recently, I noticed some significant differences in the setting of this overprint. However, it was well recorded in part 2 of the NB handbook that such differences were found on the 1c, 2c, 3c, 4c, 6c, 8c and 10c adhesives.
The main reason for this overprint was to create yet another set of stamps for collectors. The official reason was to publicise the granting of protectorate status by the British Government in 1888 to the Borneon territories in an effort to control the competitive land grab between North Borneo and Sarawak from Brunei.
My measurements are slightly different from the handbook. There is about 1mm in difference in distance between the words of the overprint. The stamp on the left also has the double ring Sandakan BNBC cancellation, most commonly found on the 2c which may reflect fiscal use for some sort of minor license fee. It has a faint date of 13 FEB 03.
The handbook records 3 different settings of the overprint for this value of 11.5mm, 12mm and 12.5mm.
The left stamp has a very attractive but faint blue Lahad Datu cancel. I thought it was a possible "Gayah" cancel from a distance but that would have been a very very late usage. We also have a very nice blue Jesselton cancellation, D2, but it is not possible to make out the date.