I went to the Monticello Railroad Museum Saturday, July 7. It was a perfect day and I had a great time. They had a display of railroad drumheads. I had never heard the term before. These things were placed on the back of passenger trains to identify them. They were also lit so they would be visible at night. I suppose they were valuable to railroad personnel - it might have been a way to know which train was what, but I imagine they were also used as advertising. It's hard to tell from the pictures, but they were about 2 feet in diameter.
I like the idea of naming trains. I also thought they were beautiful as art - simple, bold, my kind of graphic design!