A couple of thought bubbles of how it seems to make sense to me. In the past I've replaced tyres. Removed the old one, removed the balance weights, installed the new one with the balance marks in the correct orientation, spun it up on a balancer, and it's balanced! Where do you put a balance weight if it's balanced first up? You don't! But then it looks like it's unbalanced cause there's no weights on it. Granted that's rare, but it sometimes happens.
The parts for balancing would be placed on a balancer, then a measured amount of steel would be removed, and then checked again for balance. If still out, more can be removed, but if only half a bees dick needs to be removed, re-drilling isn't required, simply a paint mark is placed on the heavy spot. But what if it's perfectly balanced when checked again, where would you place a balance mark? You wouldn't! This would happen more often than we might think because a calculated amount of steel is removed for initial balancing. It's a safe bet that BMW would put these parts aside, so if you buy a clutch pack, the balanced parts would all have a balance mark, or none would. I think it's a safe bet that your clutch pack parts are balanced and can be installed regardless of orientation. If there are balance marks, the three marks should be spaced evenly apart at 120 degrees.
Puzzling.
The cover plate may have been replaced with a balanced, unmarked one. It may have been oil soaked and cleaned by a previous owner who did a Mickey mouse job, removing the mark. Some riders aren't aware there are balance marks from the factory, especially since the repair manual says to mark the parts, and they could be black all over. Sometimes it's a thick blob and chips off with a rough handling.
True enough my description of the diaphragm spring is crappy, maybe I should have said it doesn't have to be synchronised with the balanced parts, which are not symmetrical, or something like that.
