Permission gladly granted, zenstat! Is it safe to assume that we can trace the "hollow Ink" era officially back to 76? I was always under the impression that they started around 77 with the hollow ink. Were the only 76 hollow ink models the fancy font Rock bicentennials and the rest of the normal models followed later in 77?
*edit in 2020*
The 1976 year for that flyer turns out to be inaccurate. The publication year on that flyer is October 1974 and the ad campaign isn't specific to 1976. See:
http://www.vintagedrumforum.com/showthread.php?p=460426#post460426
in a similar vein since 2017 no pre 1978 hollow ink Zildjian cymbals have come to light. That doesn't mean one won't appear some day, but in the last three years all the leads I've followed up haven't produced a cymbal with quality provenance.
*edit in 2020*
We know the ad campaign was 1976 because some of the ads are dated. We believe that some (most?) of the cymbals produced in 1976 would have the Bicentennial ink. But we also know that Zildjian start production a year before they are released so they have them in stock ready to ship (pers comm. Paul Francis). We also know that during some periods the ink and trademark stamp were added when the cymbal was selected from the vault to fill an order, not when it was hammered and lathed (pers comm. Paul Francis). I don't have a "date of last use" for the Bicentennial ink stamps so they might have been used in 1977 or later. It's hard to be sure about that sort of thing because "year purchased new in a retail shop" is sometimes a later year than "date of last use in factory".
The Rock Hats (14", 15"), Rock Ride (20", 21") and Rock Crash (16"-19") all started in 1973 so they will have ink appropriate to that period. I'm not sure whether the Rock 21 was around before the 1976 Bicentennial campaign. And after the Bicentennial campaign all the Rock cymbals reverted to the ink which was the standard for the 80s -- or maybe late 70s followed by the 80s? Again it depended on how long the Bicentennial ink was used in the factory.
There is some evidence that the hollow Zildjian ink on the bottom was in use before 1977. The official years given by Zildjian are
Open (aka Hollow) ink Zildjian on bottom: 1978-1982
Solid black ink Zildjian: late 1982
but I've heard from a few trusted sources that they are sure they purchased cymbals with the Hollow Ink Zildjian in 1976.
All of which is why I always say "remember there is a ±2 after any year because we can't really get things more accurate than that".