Mathew Brady print of Lincoln two weeks before his assassination on his boat on the Ptomac with Generals Sherman and Grant and

I'm just trying to find out what it's worth.
My dad was stationed in Virginia during WWII as an M.D. He walked through Arlington National Cemetery every day on his way to work. I figure he purchased it there. We're going through stuff from his house and found it.
It says they are discussing peace terms.