The backglass price depends in part on the following (in addition to condition):
1. No stars (rare, more expensive)
2. Small stars (rare, less expensive than no stars)
3. Large stars (least desirable, cuts price.)
So, why stars? There are several controversial images in the backglass - some see-through tops showing too much for the censors of the time, someone with their hands down a guy's pants, you get the picture.
The first fix was the small stars. When that didn't placate the censors, the larger star backglass came out, and pretty much "covered" their concerns.
So, which one do you have?