Allie X's signature cropped from the postcard which comes with The Story of X Chapter 1. It is not handwritten, but printed.
Allie X
The Story of X: Chapter 1 <a rel="nofollow" class="external free" href="https://web.archive.org/web/20150602182917/http://phi.boutique/the-story-of-x%3A-chapter-i-allie-x-01/dp/732">https://web.archive.org/web/20150602182917/http://phi.boutique/the-story-of-x%3A-chapter-i-allie-x-01/dp/732</a>