Here are the inside cover and first five pages of John Robert Derbyshire's New Zealand passport, issued in Wellington on October 23rd, 1930. The other pages of the passport are all blank.
I am not clear why Dad acquired a passport in 1930, or whether he had one before that. Since he listed his infant son Noel on the passport (Noel then ten months old), presumably he was planning his return to England. This is at odds with what Dad told me, though — that he decided to return only in 1931. I suppose these tiny mysteries will never be resolved.
The signature on the inside cover is that of Charles Bathurst, 1st Viscount Bledisloe, who was Governor-General of New Zealand from 1930 to 1935. There is a biography of His Lordship, and an actual recording of his voice, at The Encyclopedia of New Zealand website.