"With the onset of America’s participation in WWI, Truman rejoined the Army National Guard. Before going to France, he was sent to Camp Doniphan in Oklahoma for training where he also ran an on-base canteen with fellow serviceman, Edward Jacobson. Jacobson had worked previously as a clothing store clerk.
After serving as a battery commander in an artillery regiment in France, Truman and Jacobson opened a haberdashery in Kansas City. It was then that Truman met Léon Gallet (1899 – 1975), a Swiss gentleman traveling across America to find new outlets for his company’s Swiss timepieces. Being of about the same age and sharing similar interests, including a serious involvement in Freemasonry, the two men became friends.
When the time came for Léon Gallet to solicit the American military for purchase of his company’s new pilot’s wristwatch, Gallet contacted his friend, then a US senator, for help. It was during ensuing discussions that Truman requested from his personal experience as an artillery officer, that the telemetry scale found on the dials of the 1st series of watches, be added for timing of munitions blasts.
Truman’s assistance in procuring a military contract for his friend from Switzerland was initially unsuccessful. While Gallet’s wristwatch, with its extremely durable design, highly accurate elapsed time recorder, and time zone calculator was the ideal accessory for long bombing missions across Europe, the watch’s advanced technology proved too costly for the military’s limited spending for mass- issued timepieces. Instead, Truman’s recommendation resulted in the issue of Gallet’s Flight Officer on an “as needed” basis, where the watches were purchased individually, or funds were provided to servicemen for private acquisition."
In spite of initial resistance, hundreds of Gallet’s watches took to the skies on the wrists of US and British aviators during WWII, with President Truman donning a Flight Officer during his term as America’s 33rd president.