Took me some time to figure this out and the answer lay with Scores suggestion that there are multiple LCDs for the 8520.
Before you purchase a new LCD for your phone disassemble down to the lcd and check the model number on the back of it.
There may be a 2mm lining of black tape on the top and bottom so using a case opening tool peel back this tape to reveal the last few digits.
The magic number for me for repairs of this model of phone is 113/114
If you have the wrong part you may get;
A white screen
or
Fuzzy colours on screen with a faint border of the apps.