Good afternoon,
A careful study of both the original card and Carols link show them to be absolutely identical. I think the printer has taken a naval postcard, possibly battle of Jutland so pre American involvement. They have then pasted on the field gun and plane, made a cutout which includes around the flags. Then they have reprinted the result to be used as shown.
A look at any photo in the same front with a photo showing same background would perhaps tell us a lot. Also finding the original naval card if my theory is correct.
John915