Malcolm,
The support washer fitted the seals that were supplied for the flywheel, but in civvy use, that particular make/type of seal is difficult to locate now, although it is a common size, it is the profile of non pressure side that differs, not allowing the washer to press up against lip of seal. There are ways around it, by making a support washer to fit seals that are obtainable. Some people have turned the washer around. Personally, I have always been able to locate the correct seals, so cannot vouch on other methods.