I have had this lower right part sheet for some years. It shows the varieties of flaws of the overprint fairly well and gives an indication to their position on the sheet.
Also on this sheet, one can also see "broken bar" variety on the right in stamp R7/5 and "broken bar" on the left in stamp R8/8.
There are a few like this on the sheet with an "empty crown" where the details of the crown are indistinct.
The top right stamp shows a "tower" among the trees which is unfortunately not present on the part sheet and so could be part of a one off ink smudge during printing. I have examined a full cypher sheet and is unable to localise this flaw. If constant, it maybe only be present at a certain order and printing of this value.
The record shows the were 4 orders during the life of this issue. For this 1c the orders were 1937 1 million, Aug 1941 1.5m, Sept 1941 2m and Feb 1947 1.5m. There were 3 frame plates and 1 vignette plate used.
Reference: Sarawak Journal vol 35 page page 94-96