Vintage Zildjian (Made in USA) Avedis Zildjian 20" Medium Ride. No cracks, beginnings of key holing, no dents. No ink logo present.

 Best we can identify is this is a 1960s Avedis Zildjian cymbal based on the stamp, see archival page pictures above. It is similar to the 70s stamp as well as the Small stamp (57-59) but the 70s and Small stamp do not have the 3 dots in the Arabic logo. It also shares many of the characteristics of the CO stamp except the o in the CO on this stamp is not capitalized as on the CO stamp. It is definitely not 94 or newer as there is no laser-engraved serial number. And it does not even come close to any of the other stamps used by Zildjian over time. Personally it is exactly what I remember from the 70s as a young drummer starting my professional playing career. But that does not seem to match up with the archives nor the opinion of the "experts" and "historians". Nor am I a Zildjian expert as I have always pretty much been a Paiste guy. Overall great sounding cymbal, very musical with a lot of Ringoish sound and texture to it. It definitely exudes that 60s British invasion sound. But can absolutely cut through when really layed into and make you feel the early 70s Ala Kenny Jones, Faces era.
Archival page photos are for reference only.