Is that a picture of the actual glass or is that a picture of the artwork file?
To have a glass like that screened, you need to make up the 2 different colours.
This looks like a PS file and the darker areas are PS black painted in as fill
That is a picture of the actual backglass 
I am truely astounded!... The harsh black would have been from a build up layer.. possibly a couple. The actual shape of it though is someone making these files on a computer hand drawing short cuts.
Thats very sloppy work... bloody well spotted though!
