Are there two types of chainguard for the C15. (1964 SS80) Chainguard I have has a solid support between the two sides of the guard, but my swing arm has a solid lug that fits between the two sides of the guard, so obviously it will not fit. Hard to see in the parts book. Thanks
C 15's & B 40's shared a frames and tinwear. There were quite a few different frames and variations, competition , trials SS and then the late all welded frame. By now there is absolutely no reason to think that any 2 parts on any C15 left the factory on the same machine. 40-7701 or the cometition models and 40- 7712 for street models.
Seamus, It is highly likely that you have the correct chainguard. The C15 road bike frame used the chainguard as you describe with a solid tube at the rear (closest to the shocks) mount lug. Just the guard mounts to the inside of the swingarm against the lug, not straddling it. Thus the tube so it doesn't crush when the mounting bolt is tightened. Try it on and you will see how it works.