Question About Pixelation and Older Photographs (from 1980's

[dss174]

Hello,

I recently purchased an autographed Jim Henson 8x10 from 1987. It's signed by him in green sharpie but the photo appears pixelated, not as crisp as one would think. Back in 1987 is it realistic this would happen to an 8x10 photo? I thought that was a fairly new phenomenon with digital reprints and what not. Is there a tried and true way to tell if this is newer photo paper or any other hints?

[fromuk2014]

I was thinking the sharpie pen was made after the date but Google says it was made in 1960's and I'm sure low quality prints are possible from then so it could be real.