According to "Flat to the Boards" by Dick Messenger (and Douglas Wood) the 1922 NZ Motor Cup was run on 11 March 1922. It was scheduled for 25 February, but was postponed due to bad weather, and the next suitable tide was a fortnight later.
This book came out in 1986 and is a comprehensive record of NZ motor racing up to 1940. Quite probably many of the pictures in this thread are also in the book. I must have a good look.
Stu Buchanan