I have not correctly typed the paper on which these stamps are printed. It has the same watermark as the 1E4, but was used in 1939. The stamps are typographed. This paper is very thin and has a slight coating on the printed side. It could be classified as a clay paper,and I am leaving it as the CL1A; it is a 1E4 type paper, but it is not 1E4.
I show the 5c. It is a much more common stamp than the 10c Brown.
Here is a 10cBRt1E4 used in 1939.
Here is a vertical pair.
The watermark is best seen on the back of this vertical strip of three.
This 10c Brown is rare used, and even scarcer on cover. However, the claims of extreme rarity that are sometimes made I think are the result of a miss-classification. This stamp definitely fell through the cracks of all classifications to date. The references to date mention an early printing of the 10c Brown from 1939 but in offset, and we now know that this stamp is typographed.