My thoughts about this picture...
I remember when this issue of MODEL BUILDER magazine
arrived in my mail box. I was surprised and excited because it was the
first artist's depiction of a Robertson CAM-2 DH-4 that I had ever seen up
to that time. In addition to being an accomplished aviation artist,
Bob Benjamin is also an avid model airplane builder like myself. He's
got a nice web site showing some of
his other aviation art that you might want to check out. I met Bob Benjamin
at a model airplane event not long after this cover appeared, and I talked
to him about it. Bob said that when he painted this picture he had
very little specific documentation about Robertson DH-4s to work with.
Most of his inspiration came from a book entitled "FLYING THE MAIL" (a volume
of the Time-Life "EPIC OF FLIGHT" series) and from the movie "THE SPIRIT OF
ST. LOUIS". In the book there is a story about Lindbergh and CAM-2,
as well as numerous photos of other DH-4 mail planes. The are some great
air mail scenes early in the movie, utilizing a DH-4 that was owned by Tallmantz
Aviation, painted for the movie in Robertson CAM-2 colors.
Tallmantz DH-4 used in the movie "THE SPIRIT OF ST. LOUIS".
Both the Tallmantz DH-4 and the DH-4 in Bob Benjamin's painting carry Robertson number "110". Notice that the number is located back close to the leading edge of the bottom wing, while the original Robertson DH-4 #110 had the number further forward on the cowling. A small difference, but one that shows that Bob was most likely using the movie airplane as his main reference. There are other clues which lead me to the same conclusion.
Both the movie airplane and Bob's painting show extended exhaust pipes. The pipes extend all the way back past the trailing edge of the bottom wing, then turn sharply down, past the bottom of the fuselage. Historically many DH-4s used in the air mail service, even later Robertson DH-4s, did have lengthened exhaust pipes. This was done to keep the bright exhaust from blinding the pilot at night. However, the four original CAM-2 innaugural DH-4s, including ship #110, did not have long pipes. They had short length, stock military exhaust pipes.
Although they don't show in the above photo, the Tallmantz DH-4 had two landing lights located underneath the bottom wings, exactly where shown in Bob Benjamin's painting. You'll have to re-watch the movie "THE SPIRIT OF ST. LOUIS" to see this. Watch closely in the scene where Lindbergh's DH-4 is being swung around for takeoff during a snow storm at the Peoria airfield. You'll see the landing lights in that scene.
I don't know when landing lights were actually installed on the original Robertson DH-4s. While he doesn't mention landing lights, Lindbergh does state in "THE SPIRIT OF ST. LOUIS" that red and green navigation lights were added in September 1926. Perhaps the landing lights were put on at the same time.