This miniature sheet of 9 on paper without gum is based on the 8c Dhow of the 1894 issue. It was also printed in another 2 bicolour combination but I am not sure whether they are also in sheets of 9. I find this one has particularly attractive colours. They were used as trade samples by Waterloo & sons Ltd and has a security punch hole. They were not specimen stamps in the sense of being sent to countries belonging to the Universal Postal Union as they were not postage stamps.
It is difficult to know how rare they are. My guess is that they are tightly held by being quite desirable especially in NB and thematic collections alike.