Hey I just became aware of this thread- my mother-in-law saw it somehow.
The cymbal on ARS belongs to me and it is an A. Zildjian, 30" in diameter. I've owned it since the early 90's. Got it from an ex-drummer that acquired it in the late 70's - from where I'm not sure.
It's got the Zildjian stamp but no ink markings. The bell is disporportionately small considering the size, and the sound of the cymbal is quite musical with the response and articulation of a medium ride. The overtone lasts for almost two minutes if struck hard!
My feeling is that the cymbal was made in the late 60's, early 70's. A friend of mine asked a rep at Zildjian about it once and the rep wasn't aware of any cymbals of that size specifically but said that Zildjian used to make some large rides for the drummers of Stan Kenton's big band.
The ARS appraiser told my wife that he couldn't think of an application for it except maybe the circus- which doesn't seem too far fetched.
Anyway I thought I'd let you know what I know. Would love to hear any lore pertaining to 30" ride cymbals.
Cheers,
PA