Hello All - It is pretty simple really ... The coins mentioned above by
oynbcn were only released in Sets. From 1967 to 1970 New Zealand coins that were released in sets came in 2 different ways.
Some were just normal strike coins but placed in a thin plastic cover which had a Pink Label. Some were the same coins but polished or sometimes known as Prooflike. They were basically just "Specimen" uncirculated coins also placed in a similar thin plastic cover with a Blue label.
Here are 2 examples of the 1967 sets in Pink and Blue labels.
It is easy to tell them apart if you know a little about coins when you see them in the flesh in the set.

But if they have escaped into circulation it might be difficult.
From 1971 actual real Proof coins were issued in hard cased encapsulated plastic. The Bu sets were still issued in the thin plastic covers but no longer had the Pink Labels.
So with regards to the coins that oynbcn mentioned above this is the answer.
1969 New Zealand 1 cent - Was only issued in Sets, There were 2 sets
BU set 50,000 (Pink label), BU are just normal strike coins but Uncirculated.
Specimen Set 50,000 (Blue label), Specimen are what are also known as Prooflike or Polished coins.
1977 New Zealand 1 cent - Was only issued in Sets
There were 2 sets - BU set 20,000, Proof Set 12,000.
1970 New Zealand 2 Cents - Was only issued in Sets, There were 2 sets
BU set 30,000 (Pink label), BU are just normal strike coins but Uncirculated.
Specimen Set 20,000 (Blue label), Specimen are what are also known as Prooflike or Polished coins.
1979 New Zealand 2 Cents - Was only issued in Sets
There were 2 sets - BU set 25,000, Proof Set 16,000.
1968 New Zealand 5 cents - Was only issued in Sets, There were 2 sets
BU set 35,000 (Pink label), BU are just normal strike coins but Uncirculated.
Specimen Set 40,000 (Blue label), Specimen are what are also known as Prooflike or Polished coins.
1977 New Zealand 5 cents - Was only issued in Sets
There were 2 sets - BU set 16,000, Proof Set 11,000.
1979 New Zealand 5 Cents - Was only issued in Sets
There were 2 sets - BU set 25,000, Proof Set 16,000.
1983 New Zealand 5 Cents - Was only issued in Sets
There were 2 sets - BU set 25,000, Proof Set 18,000.
1984 New Zealand 5 Cents - Was only issued in Sets
There were 2 sets - BU set 25,000, Proof Set 15,000.
1970 New Zealand 20 Cents - Was only issued in Sets, There were 2 sets
BU set 30,000 (Pink label), BU are just normal strike coins but Uncirculated.
Specimen Set 20,000 (Blue label), Specimen are what are also known as Prooflike or Polished coins.
In Numista we always separate BU Sets from Proof Sets in all countries, not just New Zealand.
I hope that this answers your questions.
Take care and relax guys.
Master Referee - See my profile for what I collect.