From that same website, it linked through to that picture.
"6) Poorly modifed Fender Mustang from the early days. Its control plate and weird bridge currently reside in a pink suitcase of Kurt's (15)(59).

Also, despite how many pictures appear, Kurt never used a white Mustang. The sonic blue tend to look white, especially with the crazy light show NIRVANA had during the "In Utero" tour."
I didn't even notice it was linked through a website, I got the picture from an article, but thanks a lot!