There doesn't seem to be consensus. Same with Supers.

Pasite-only wiki says NS12

http://www.paiste-only.com/paistewiki/index.php?title=Ludwig

RaBe says B20 like the Super

http://home.mnet-online.de/cymbalism/cymbalism/cymbals/series/Paiste.html#ludwigstd

This German (I think -- could be Swiss German) site says NS12

http://www.nf-drums.com/paiste_fanpage_paiste_timeline.htm

but it also distinguishes between two sorts of Super (one B20 one B8) Super Formula 602 vs just Super. Meanwhile, the Pasite-only wiki says Supers were first NS12 then B8.

http://www.paiste-only.com/paistewiki/index.php?title=Super

Now the RaBe page is quite old, and more may have been uncovered since then. This might be what is reflected in the other two sites.

If you have one (or access to one) check it out and let us know what you think. I hear people claim they can correctly assess the material a cymbal is made from by having hands on it. I don't know how that claim has been evaluated. I do know that some cymbals can look quite different in color from one photo to the next due to changes in lighting and color balance. So I would give low weight to evidence from photos only compared to hands on. And of course the "gold standard" evidence comes from having a lab do an analysis on a piece of the cymbal.

The Ludwig 3-stars are NS12 cymbals.

Now, is there a chance they made a few examples out of B20? sure, anything is possible, it is said Paiste did experiment with different alloys in its cymbal lines back then, but not likely imo. The pricing of the cymbals doesn't bear that out.

Also the SUPERs were NS12 and then later B8 not B20.

It was the Super Formula 602s that were B20. They were the precursor (1957-1959) to the regular Formula 602 line.

I have a set of Ludwig Paiste 3 star cymbals and they are NS12. They sound really nice as well.

I have one Swiss Ludwig Paiste and it is clearly NS.

I've got a handful of 3 star cymbals and I love them. I believe all of mine are NS12.