Here is the artwork I have.
As I recall, the background was clear, so the lettering and the large "J" might be blue with the large "L" in white (from your photo).
Illinois plate? I'm not sure. Seems to have a plate frame covering where "Land of Lincoln" would be. But, Illinois, back in the day, used a Letter (then two letters) then numbers kind of like in the photo.
Anyone with a guess as to its size? 2" X 3 1/2"??