Both stamps with Sandakan postmarks but the second stamp has part of the year missing. It appears that these stamps were used concurrently with the 1888 issue with the amended "Postage and Revenue" inscription. There should be some interesting postmarks found with this issue including Gayah/Gaya, Labuan and the Silam negative seals.
These are latter day cancels by favour by a friendly postal clerk using the Sandakan D11 box type or squared circle cancellations and are best avoided. D11 was in use between 1904 and 1915. There are other dubious cancellations including one that I have seen for "Heligoland"!
The well known one cent error. There is an image of a row of 3 in my previous post in July 2011.