G'day Mark,
I was (reliably?) informed that it is a Road Rocket front guard and more rounded than a Super Rocket one but I will bow to your opinion. It was on the bike when I got it and certainly looks the part.
It measures approximately 705mm across the arc. That is:- from the bottom, close to where the stay fits, straight across to the centre of the rolled edge at the front.
Beezageezauk.