Indeed a predecessor to the rather common Shimano Biopace of the 80s-only several shown here have a much more radical ellipse. The Shimano version is not immediately obvious to the eye or legs. As to the purpose, they are supposed to make it easier to turn when your legs are at the point of the circle where they can contribute the least force, as the available power of the legs builds so does the diameter of the ring--then the ends of ellipse engage during the power stroke. If you measure the distance between the points of the football, that's the effective diameter of the chainring--but should require the same energy as one several sizes smaller (if round). BTW mount your crank arms in the wrong relation to the ellipse and you're screwed.
I've never thought about it 'til now, but I wonder if it was named Biopace because it used the Golden Ratio -1.618 (or close to it). Anyone know?