Hi John
As I said in my post I have seen a lot of examples with a combination of features and yours is one of these. Early Tachy scale, later dial with double black stripe on the hour markers and later hands probably the 3rd version Heuer used. You probably know that the serial is found between the lugs just below the top surface. Its often missed and therefore often removed when the case is polished.
So the search is still on.
regards
Paul
www.heuerworld.com