This is New Zealand's largest and highest valued stamp. It is also one of the most controversial as many stamp collectors believe that rather than responding to a demand for a high-value postage stamp for documents and parcels, the stamp was a ploy to fleece collectors.
Two used examples - the right-hand from a first-day cover.
Of course, NZ Post says it quite differently. "In response to demand for a high-value postage stamp for documents and parcels, New Zealand Post issued its first ever $20 Definitive Stamp. It is one of the most complex stamp productions ever commissioned by New Zealand Post - its design is a masterpiece in montage and it captures some of New Zealand's most treasured heritage. With such an elaborate design, hidden security features, and an extremely complex production and printing method, this magnificent new stamp is truly reflective of its high face value - both here and as an ambassador on overseas parcels."