01 bonneville 12k miles. Here's a video of my bike I took while going down the road. The noise happens when I'm going slow and clutch out in any gear. It stops if I clutch in. It does it about 70 percent of the time as I clutch out. The clutch doesn't slip and it pulls well.
Just clutch rattle I think. Most clutch driving sprockets are fixed via rivet type fittings that eventually get a little loose and can rattle never ever seen one fail.
I had a 01 Bonneville and I remember that there was a frequent problem on the clutches of these early bikes. They had to be recentered and modified. Show your bike to a good dealer. Hopefully, he will remember this issue and know how to cure it.