Signed between 1987 and early 1990's. Authentic IMO.
How big is it? A 16x20 poster framed up nicely, I would put in the $150-200 range. He was a tough signature, but certainly not an impossible one. I saw him nearly 10 times over the years, a few times one on one, and he would always sign for me.
One time staking him out, he almost ran me over in the airport parking lot. He got out and laughed, and then signed everything I had.
It's authentic. It is consistent with his 1984-1988 signature style and not rushed like his mid to late 90's signatures. The value is in the $100-$150 range for this hero card.