Friend of my grandfather

This photo was among my grandmother's pictures. This message is written on the cardboard cover:"To Corporal John T. Harman from Private Samuel ?. Epstein." I can't read the middle initial and I'm not sure of the spelling of the last name. John T. Harman was my grandfather who died in 1933. He was in WW1 and spent time at Ft. Sill, Oklahoma near Lawton. The cardboard cover includes this proffessionaly printed information: "Hall's Gentry Studio Dallas Little Rock St. Louis Lawton."
My grandmother never mentioned Samuel Epstein.
I would like to give it to Samuel's family.