Many thanks guys for the comments and the tips. Now the internet forever has a discussion to refer to on this particular question.
As far as sound, OK...weird story, but I haven't heard them live and may not for some time. I live in Italy and I am collecting a set at my brother's in USA with the idea that he will bring it here as he is in the military and supposed to be sent over in 6 months or so.
I have to admit that while I have played only vintage guitars from the beginning since in the 80s there were only Charvels and Kramers with stupid tape job finishes, I have never been able to hear the difference in cymbals new vs old. I can in drums, again, because in the the 80s, the worst period for music equipment in history everything was "thunder drums".
I can hear good vs bad, and I know what I like (generally Zildjian) but unlike with drums, guitars and amplifiers, I don't seem to have the palate to know what makes old so special---or maybe better put, why new is not as good, even if they are machine turned and so forth. I am sure I am in the wrong here and over time will learn to discern old from new cymbals.
But for the time being I still have a decent reason for buying old cymbals. I buy old because I detest those huge ink stamps on the new cymbals!
Regarding size, I chose 13" because I was in London trying out Zildjians and realized that as a non drummer I felt I had more control on the 13s than the 14s.
My brother made a recording of the hats vs his 15" new beat Paistes (he got at a thrift shop for thrift shop price). To be honest I couldn't hear anything different between the ching, but I could hear that his had more wash on the edges, like Ringo's on, for example, Long Tall Sally.
Thanks again for your input, it saved me a perhaps awkward discussion with the ebay seller where I would have been the one in the wrong, it appears.