This document was kindly supplied to the Cymbalholic community by Paul Frances a few years back. That is why it ends at 2017. It is a great start but not quite 100% complete. I'm slowly (with the accent on slow) working my way through it to check it against catalogs, flyers, ads, price lists, etc. It will eventually form the backbone of a complete list of models and series for all Avedis Zildjian cymbals. This will go into the wiki with the same level of detail we have for, say, Paiste models and series:
Your question provides a good worked example. The Pre Aged Dry Light Ride 20" diameter does not have an end date. That is an omission. It is not in production. In order to pin down the year it went out of production we need to collect examples of laser serial numbers on 20" PADLRs and see when they stop. When I last wrote up something on PADLRs
http://www.threeonthefloor.com/zildjian-discontinued-k-20-pre-aged-dry-light-ride-20-cymbal-2080-grams/ This looks to be one of the later ones made JE serial (2005) 2080 grams seems about the weight most of these are in but check the hammering, looks different, almost spiral, unless it's a...
You can help me with the end year if you (or anybody reading this) has an example of a later 20" PADLR. This is how the collective knowledge is built up, one little cymbal at a time. I've currently got over 17,000 in my database.