Copied from this excellent site-
https://www.nzans.org/
"1914 - 1922 saw 626 nurses and masseuses serve in the NZANS, as well as many women who worked with, but were not members of the NZANS. All the women who were members of the NZANS were attested (sworn to serve for the duration of the war) and issued with Regimental Numbers, whereas the other women were never attested and not issued with a Regimental Number. Their attachement to Military Hospitals was controlled by the Matron-in-Chief who was also the Inspector of Hospitals for the Public Health Department.
When the nurses joined the NZANS they were issued with their NZANS Badge which had engraved on the back their Registered New Zealand Nurse (RNZN) number."