Hi Pete,
Thanks for your vote of confidence,
If you have a Supercut that is 15 years old it is likely to be the Fein FSN400E and to run Fein 8 point star centre blades. ie the ones that are sold for the Fein Multimaster at the moment you need a JFC2004 adaptor.
If you want to run cheaper Bosch blades use a JFC200 and the WSE range of blades requires a AD-05 adaptor.
There are so many different combination of blade mixes that even my engineering partner gets confused the other day after coming back from a two week break he produced me a Supercut to Supercut adaptor i expect that product to break all records as far as sales go.
I am working on a chart at the moment that will help you chose the right adaptor for the right tool and blade choice but you or any one can always e-mail me for help.
Regards,
Cliff. Joaliff Ltd.