With the introduction of decimal currency on 10 July 1967, the new 10 cents denomination was equal to one shilling of the earlier (pre-decimal) currency. The two coins were identical in size and shillings remained in circulation (and legal tender) in parallel with the new coins until they were both demonetised in 2006, when a smaller ten cents coin was introduced instead.
Large ten cent coins issued in 1973 circulated for 33 years before they were demonetised on 31 October 2006.
Krause catalogues list circulation mintage of 3,525,000 plus 8,000 proofs.
The Reserve Bank of New Zealand lists mintage of 3,533,000. Judging by other years' patterns, this is probably (uncharacteristically) combined circulation and proof mintage.
The John Bertrand New Zealand Coin and Banknote Catalogue also lists a total mintage of 3,533,000 with no breakdown into circulation/sets/proofs.