James Joseph "Jimmie" Mattern was a Lockheed test pilot, cargo pilot, a Hollywood Stunt pilot and a bit of a self-promoting adventurer. In 1932 he tried and failed to circumnavigate the globe in a a Lockheed Vega. He did set a record for crossing the Atlantic but he also crash landed in Borisov, Belarus and was taken by the soviets as a spy and interrogated. They eventually released him and shipped his damaged plane back to America. He tried again in 1933, and had to make an emergency landing in Siberia where he was literally rescued by Eskimos. After he returned to America he had a short-lived time on radio.
"Jimmy next turned up in Chicago, working on a contract for the Sherman Hotel, describing his adventures as a pilot in a nightly show. While there he met a Chicago showgirl named Dorothy Harvey. In 1934 Jimmie became the Aeronautical Director for the Pure Oil Company, and helped script a radio show (1935) that dramatized his life up to that point."The tiny blurb doesn't note the call letters but we can guess. At first I thought it might be WLS-AM. In November 1925, WLS moved to quarters on the 6th floor of the Sherman Hotel in downtown Chicago. But in 1928 the station relocated to the Prairie Farmer Building on West Washington Street. But it's pretty likely that Jimmy spoke at the 100 seat theater there that WLS had formerly used.
The Pure Oil Company called Chicago it's home. The corporation had it's own radio history. They sponsored news programming on NBC's Red Network. On the Mutual Network in 1934, Pure Oil Company bought time on WOR-AM , WGN-AM and WLW-AM for the "Pure Oil Show. " The program was 15 minutes long and ran on Mondays and Wednesdays at 9:00 PM. These were the very first radio network programs on Mutual. More here. It is highly likely that 'The Diary of Jimmie Mattern" was a Pure Oil program carried on Mutual, possibly even as part of the "Pure Oil Show. "
In 1936, two years after the radio program had ended, Pure Oil published a three volume set "for Listeners to the Radio Show 'The Diary of Jimmie Mattern'." These tiny booklets are the only real proof we have the the program existed or aired at all. Later in life the Lockheed test flights damaged a blood vessel in his brain and he became unable to fly. He retired from flying, wrote several books, and remained active in related industries. He passed away on December 17, 1988