American Class Six Was Adopted in 1991, How Come Buhari's Certificate Shows Class Six?

Ladies and gentlemen of reputable intellect, General Muhammadu Buhari's WAEC result has been released by his former sec school in Katsina State (instead of Northern Nigeria).
If this is Buhari's result, then buhari and his handlers are crooks. This statement of Result was hurriedly put together and made to look old.
1. Instead of Muhammadu they wrote Mohammed.

2. Instead of Northern region they put Katsina State. Katsina State was apparently created in 1987.
3. There are discrepancies in the subjects buhari submitted to the Army and the ones in this hurriedly put together statement of Result.
4. This obviously fake statement of Result carries a passport! Then, passports were not attached to WASC. Even mine didn't have a passport, and it was just 1994 here!
5. On this released result, they wrote SSCE/WASCE. Then there was no SSCE!
WHY THE LIES? WHEN PEOPLE LIE,THEY NEED MORE LIES TO COVER OLD LIES!

I thought Nigeria started using the American class six in 1991. Before it was class five. So, how come there is class six on the 1961 certificate of Buhari?
Can someone please enlighten me?