Your 'normal' 3d stamps are a real jungle. You'll need not only to check the watermark, but also the perforations. They could be (in Gibbons) any of SG 251, 261, 261c, 309, 309a, 309b, 321b, 321c, 332 or 341 (which would be very nice because it's priced at £650 mint).
I agree about the imperf black prints. They look like plate proofs. The Campbell Patterson catalogue (
http://www.cpnzstamps.co.nz/Catalogue.htm) would be the place to look for these - and for even more detail on your normals.