The address P.O. Box 34567 is, in fact, legitimate. It is also used on documents previously released. Check out 1stLt Bush's two DD44, Record of Military Status of Registrant, dated 9 Dec 68, and 1 Dec 69. You can download these documents from USA Today's website.
C.G. also helpfully includes the link and page numbers (see pages 10, 11, and 19).
The rapidity with which the blogosphere knocks down theories which turn out to be wrong--no matter who it benefits--is pretty impressive, no?
Now, any information about the date convention used in the memos?