there's no tellin, George, where and when those lenses came from, or if the plastic one was on the light when it was new - the new good R13 lense Bruce has is glass and it's like the lense with the circle on it, marked Guide R13, the other one had no number and the lense may be the same size/shape as a number of other tail lights, prolly interchangeable, even with Ford! ... wouldn't be suprised if by 58 they used plastic, but I've never seen one
Bill