Greetings,
I picked this up today used for a good price. Based on my research done here at the forum (thanks zenstat), I understand that these date from 1982-1985 or so, when Robert Zildjian owned Tosco and was producing cymbals in Italy.
This one does not have any engraved stamp anywhere, and there is no mention of Tosco anywhere either. It has two red ink stamps on top, one that says "Chinese" and the other is the size, first in cm then in inches (22"). The bottom just has a red "Made In Italy" ink stamp.
This is a very cool cymbal. Much more like a Swish or Pang than a true china. The bell is rounded more like a Swish, and also it has warm stick attack and the stick attack is not harsh or brash like on a lot of chinas, almost like you are hitting it with a multi-rod than a stick. It sounds very similar to an older A. Zildjian.
I don't know that I have ever seen a "B 20 by Sabian" china before, so I thought I would pass it along.