Not sure about that...
Some of the 70s
zildjians had an outlined logo
The 80's cymbals were a solid black logo and the choices were still limited but this is around the time of the family feud between the two brothers.
Zildjian started making all kinds of different cymbals and the
Sabian company had been formed by Robert
Zildjian. They too started with all kinds of different lines of cymbals.
Basically what you are looking at here is that A's and K's can be no older than about 30 years or so. I don't know when each line was introduced but that should give you a rough estimate. As far as dating a cymbal according to design I doubt there is really a way to distinguish an A
zildjian made ten years ago compared to one made twenty years ago.... I could be wrong though.