In 1917 the US government set out a roundel to be used on US Army aircraft. This roundel would be replaced in most instance by a roundel based on European use, only to be reintroduced in 1919, but with different proportions. The center dot on this version is 1/3 of the diameter - on the later version it was reduced to being bound by lines connecting the inner points of the star. Note that the colors specified matched the US flag (Old Glory Red, and Old Glory Blue), unlike the later colors, particularly the blue, which was darker on the later roundels.
Own work
NiD.29