The story line with Potter and his friend repeats a story line from season 5 "Ping Pong."
Colonel Sherman Potter (Harry Morgan) and Colonel Woody Cooke (John McLiam) are veterans of at least three wars. They first met in World War I (American involvement 1917-18), served in World War II (American involvement 1941-45), and were both deployed to Korea (American involvement 1950-53).
The music on the record that Charles is attempting to play is "Kindertotenlieder" ("Children's Death Songs") by Gustav Mahler which he starting composing 1901, after a health crisis made him contemplate his own mortality.
Since Gary Burghoff left M*A*S*H, Radar has no longer been seen at the beginning of the opening credits, But in this episode, his shoulder is seen briefly at the left of the screen.