Hi Bren
A good question ! Bit of a "curly" one too.

Can't answer it with certainty either.
Archives (Wellington) in their helpful little booklet (" Card Indexes") suggest that more information can be found in the help-binders (in finding aids section) .... or "ask the desk archivist".

(Dates of passenger and immigration lists which have been indexed, also given in booklet.)
Incidentally, all those "shelves and shelves of boxes" (or the "boxes on those shelves and more shelves" ) I thought, contained the REPRO passenger lists .

[Now have a link for a chap who apparently holds a passenger list for "Indian Queen" .... am awaiting his return email].
Lu