Your trays look very interesting. These trays were originally made in 1916 and would fall in the era around World War I, as you were told. The larger, a serving tray, was 8-1/2 x 19 inches. The small one is a change tray, measuring 4-1/4 x 6 inches.
Reproductions of at least the large tray were made in the 1970's. I could not tell for sure if what you have is new or old, but from what I could see in the picture, it looks like the large tray is authentic.
I can't really tell much about your change tray from the picture. An authentic 1916 change tray is worth $275 in mint condition.