I think that's what happens when the black ink was on there for some years, then was removed. What you see is the ghosted image and it persists because during the years the black ink was present the surface of the cymbal under the ink experienced a different environment. Here are some examples from my ongoing ink research collection. The first cymbal shows the transition from some black ink to ghosting as it is partially removed, followed by a couple of cymbals showing the full ghosted model ink.

20" 60s MEDIUM RIDE

[img]http://black.net.nz/avedis/images/ink/20-med-stamp.jpg[/img]

20" 60s MEDIUM BOUNCE 1932g

[img]http://black.net.nz/avedis/images/ink/20-1932-stamp.jpg[/img]

22" 60s MEDIUM BOP 2948g

[img]http://black.net.nz/avedis/images/ink/22-2948-stamp.jpg[/img]

The ink pattern on your cymbal indicates 1978-late 1982 according to my research at this point. In late 1982 Zildjian added diameter ink under the model ink, plus the solid Zildjian ink logos. Based on the ink changes, it seems likely that what we call the 1970s stamp actually lasted right up until 1993, although there was a time from 1982 where the CO stamp coexisted with the 1970s stamp. I'm still working all that through, and my web site needs to have the years updated although the years are all still within the ±2 I suggest people think of for any specific year estimate.

I am collecting weights for as many of these cymbals with model ink as I can get, from different production eras. I would love to know the weight of yours to add it to my research. Here is what I've got for 18" cymbals with the 1970s stamp which have both weights and model ink:

THIN CRASH 1337g-1376g

MEDIUM THIN CRASH 1448g-1454g

MEDIUM CRASH 1350g-1581g

THIN DANCE 1390g-1400g (uncommon model)

LIGHT RIDE 1316g-1576g (uncommon model around by 1980)

CRASH RIDE 1696g

ROCK CRASH 1664g

MEDIUM RIDE 1597g-1763g

That's just a clean spot left behind after the ink had faded. It could be late 70's - mid 80's if I'm not mistaken. Drumaholic or Zenstats would know for sure.