New Zealand Coins To Grade

Penny VF, half crown F.

The alloy of the half crown is known as 'quaternary metal', which is an alloy of 50% silver, 40% copper, 5% nickel, 5% zinc. Four metals made up the alloy.

The planchets for the .500 silver coins were blanched (whitened) in an acid, then rinsed thoroughly. This process leached the zinc and copper from the surface of the coin, thus chemically enriching the silver surface layer.

When the planchet was struck, the slightly spongy surface regained the hardness of the untreated alloy, but the coin now had a much more silvery appearance, with a higher percentage of silver in the surface layer. The coin was also a little less chemically reactive in circulation.

Nevertheless, as the high parts of the design wore down in circulation, the poorer alloy shows through, and that explains the discoloration on the worn parts of the coin.

The penny, being of a consistent alloy all the way through, does not show these wear characteristics.

sel_691 : Wow! That's a great piece of information.
Regarding the grade of the half crown, I feel its a VF. I am still a beginner grading coins and the rule by which I grade a coin VF is when all the major features of the coin are visible. Is that a good rule of thumb to grade a coin VF? What am I missing?