Personally, it doesn't look like some of the authentic ones I am familiar with. Here is my Clipper autographed baseball that I know is authentic, because when I was a young whipper snapper I waited in the longest line of my life at a sports show in Atlantic City to get it sometime in the 1980s.
I haven't seen many 'graphs where the "i" in Di was seperate. Usually he skipped it and the "M" in DiM started with a downward slope.
Also, when get does his "gg" in Maggio, I have seen the "g" starting coming up from the bottom, and not over the top.
Such is a similar in Mantles' autograph. The second "hump" in the "M" rotates over more than the first hump and makes it look shorter than the first.
Anyway, I'm no autograph expert, but I collect them. For 99% of the time, I get them in person. If I'm buying secondary market, I learn as much as possible about authentic and fakes so I can make an educated decision. Personally, I would not move on the 'graph you posted.
Here is my DiMaggio:
