A privy is simply done by the Perth mint to primarily bypass a "maximum mintage" such as the lunar coins for example. Everyone knows that the Perth mint can only make 300K silver 1 oz lunar coins per year. It is written into law I believe not to go past this mintage. If they were to add a design, it wouldn't technically be the same design, but rather a redesign and therefore they can make as many of the redesigns as they want to. The Perth mint, from what I have read on here, really soured the community with the dragons when they came out. Since it was a popular design to begin with, they very quickly sold out and needed a way to make more.....henceforth.....a privy was born!