Bumping this topic. At a stamp show today, one dealer had about 100 covers of the first New Zealand - USA flight in December, 1937. The fronts were all postmarked December 29, 1937. The receiving mark on the back is San Francisco, Jan 6, 1938.
Knowing about the COQK variety, I carefully looked through each. I was able to get 2 covers, each with one copy, as shown below. Due to the cancellation date, I am assuming Scott 215 (SG 589a). If it was Scott 197(SG 568a) it would be worth considerably more.




It should also be noted that this is one of the more difficult issues to check correctly for perforations. It is actually stated as 13-14 x 13 1/2. This means the horizontal perforations are 13 for one half the length, and 14 for the other half. I don't know how this happened, but it is quite confusing.