If all the holes were slotted, it was probably made by Fostoria and not Ford. They were an early replacement company (like 30’s, not 60’s) and all the fenders I’ve seen had slotted holes where Henry’s had round.
I remember seeing some “NOS” Fostoria fenders still in boxes at a swap meet in the 80’s. IIRC they also had Fostoria stenciled on them somewhere.