There's indeed some confusion here, and my flippancy has not done much to dissipate it.
Pete's CSK washer is for the
upper fulcrum shaft, which as far as I know has abrupt shoulders - from my car seen above, these are new, but the 30-year old ones are the same - and so no need of a CSK washer to cope with any major radius.
Steve's pictures of shafts are for the
lowers, seen above, which are asymmetrical to a far greater degree than his picture suggests, a full 8mm, in that these shafts carry triangulating arms of different thicknesses (approx 5mm difference) plus there is an extra 3mm washer thickness on the rear end.
On my car the dimesnions are 89mm for one end and 97mm for the other, approximately.
None of the 5mm thick "end" washers (C8693/1, under the castellated nuts) from the lower fulcrum shafts on my car has a chamfer to cope with the pronounced taper transition on the shafts.
They look very period, which doesn't make them right, and I'm not convinced the LOWER stamped on them means very much in terms of being official.
None of the pictures on the web for C8693/1 (or C8693) show such a CSK either.
Can anyone throw any more light on these please ?
I think this does matter, as the crush on the rubbers will be very influenced by the way the end-washers accomodate, or not, these tapers.
There is nothing I can see in the Knowledge Base about this.