If the older,larger fan blade measures approximately 17+ inches blade tip to blade tip, that would be an original size. And I think the shape indicates original also.
The old fan blade (larger) measures 18" tip to tip and 3 1/2" at its widest on the arm of the blade.
The new fan blade (smaller) measures 15 7/8" tip to tip and 2 1/4" at its widest on the arm of the blade.
