I bought a small wooden box at an estate sale today and there was a stock certificate in it , is it mine now?

Just happened like half an hour ago I saw this box and bought it. Inside was this stock certificate and it says there’s 200 of them bought in 1987. I tried finding the company and I might have found it at $70 a share right now. It’s registered the owner to I assume the person who had died at the estate sale, but I’m not sure. Do I own it, can I sell it?