Does a High School Diploma Require a Seal?

My husband was home schooled all his life by his parents, which means he graduated and has a High School Diploma, but he never really received one from a school system. A job requires that you have the diploma in hand, so we are trying to make one for him. What is the best way to make a real looking diploma, and does it require any type of official seal? Any help would be much appreciated! Thank you!