Sessions raced in the Indianapolis 500 from 1966 - 1975 His best finish was 2nd 1973
The yellow strip on the right side of the image is in the actual picture and was probably used as a border to separate the driver pictures.
Signature is in bold blue ink pen and would rate 9" - 10". There is a couple of tear at the bottom middle one that goes from bottom edge to the first of the second "s" in his last name.
In 1977, tragically Sessions died in a snowmobile accident in Minnesota
I will be listing several other similar signed driver pictures.