According to Potter and Shelton there were four printings of this value:-

1938 Grey-black and deep purple-violet

1941 Black and deep violet. This was classed as a 'Colonial Release'.

September 1943 Black and deep violet and Black and Violet

July 1947 Black and Violet

I could find no record of the 1941 Colonial issue in the Crown Agents records in the British Library.

I will try and add the details of the 1947 issue at a later date.

Date of dispatch and Req number	Sheets Ordered	Sheets Printed	Stamps Printed	Dealers	Comments
3613/4 3.3.38	700	736	42,000	12,000	12,000 to dealers and specimens. Sheets of stamps to be interleaved with wax paper in parcels of 100's.
4390/1 19.2.43	100		6,000		For Dealers
4390/4 15/9/43 & 9/12/43	500	525	30,000	10,000	Urgently Required Interleaved with wax Paper