Sorry it took so long to answer your question. The only NZ silver coins are from a very limited period 1933 to 1946 so that is why so many seem to be from the WW11 period. The NZ silver coins are only 50% silver content. The large bullion coin being 99% pure silver is an exception but that isn't currency and is should not have been found in the wild. The English silvers are .925 silver until 1919, then they became 50% silver and we find a quite a few English silvers as NZ only got its own currency in 1933. As we are close neighbours with Australia we find many Australian coins too.