Bryan - My thought is that there is a strong possibility this is secretarial. I'm just not a fan of uninscribed photos of him generally. He's really a tough one from the mid. 1960's onward. Maybe David L., Joe W or some of our other knowledgeable folks on him will see this.
Many thanks for your input
The way the photo is signed sideways along the right border made me think it could be Newman's hand
I also believe this is a secretarial signature.
I agree with Etienne and Joe W..
It's definitely a secretary