Single hole valances were on standard TTFs probably until G-suffix introduction. The TTF also had one towing eye so it makes sense. When the 3500S Automatic for the North American was introduced Rover added an extra eye to these cars for lashing purposes, hence the second hole. Then they standardized that across the range until the end of production.
Conrad D. Conelrad, you might have something unique from very early production cars or even pre-production. Question, does this valance have multiple vertical slats in the small air intake on the top or only one?