I came across this watch while searching for a 2447 T. This scale might be from a Nivada Taravana chronograph. This is what is interesting to me because everyone will tell you about the common interests between cars and watches. What if this ring was added "in period' to create the ultimate sports/racing/rally chronograph which it is. A decimal timer AND a tachy scale. Heuer should have done this but they didn't. If someone found an original owner 1968 911 with ST style Minilites, Scheel seats, Rally Master clocks and big Cibie lights on the hood or an original owner 2002 with an Alpina intake, very few people would say, "this is not original and someone is trying to pull one over on us". These would be very desirable automobiles.To me, this watch hasn't been changed or put together, but has been "hot rodded" with an added part and this addition has clear benefits to it's performance. This watch can be brought back to "stock" fairly easily, but I think it is cool the way it sits.