[COLOR="DarkRed"]NS12 is often called nickelbronze, or (oddly) nickelsilver.
It is a Copper, Zinc and Nickel alloy, I believe.
Historically, cymbals are Bronze which is an alloy of Copper and Tin. B20, B8, B15 are the 3 most common these days, although Meinl also has a B10. The number being the % of tin in the mix. B20 (Bell Bronze) is the most widely used.
(Technically, the B20 designation really is "CuSn20"...but that doesn't exactly roll off of teh tongue, so B20, etc. is how it is typically referred to...)
Brass is Copper and Zinc.
So, an NS12 alloy is basically Brass with the addition of Nickel.
Nickelbronze (NS12) seems to have come into use in Germany and vicinity. It was the first cymbal alloy which could be stamped out of sheets of metal. So, Paiste used it on their earlier cymbals, probably for ease/efficiency of fabrication more than anything else. Usually when you come across an old NS12 cymbal, it is from Germany or environs.
Their sound is a bit limited; kinda metallic, not the most responsive under the stick, and too bright for my tastes...
But, I have had some old Paiste NS12's which worked quite well...particularly the hi-hats and some crashes. But most are, as I said, limited in their sound and generally not sought-after much, anymore. [/COLOR]