I have 12" X 18" Fire Chief and Sky Chief pump plates that have "Made in USA" in the lower left corner and the month/day/year in the lower right. The 8" X 12" Sky Chief pump plate I have has "Made in USA" in the lower left and just month/year (3-42) in the lower right corner.
(I don't have the 12" X 18" signs here to look at, but do know the years are 1948 and 1959)

Pat