The caption to this card reads:
"RANGITIKI" (NZSCo) IS ONE OF THE BIGGEST MOTORSHIPS  IN THE NEW ZEALAND TRADE VIA PANAMA.
This same card appears elsewhere on the internet identifying her as the RANGITIKI's younger sister, the RANGITANE. 
It is most unlikely that the same one funnel steamer was passing both ships at different times in the same place.  So which caption is correct?  Did the company make a habit of arbitrarily identifying each of the three 'Rangi Boats' on the selfsame images?  Another very similar (but cropped) picture appears on page 18 of the World Shipping Society book, "Crossed Flags" also identifying the vessel as the RANGITANE.