That is interesting. I wonder what is different between your machine and the other machines that take the flat discs. As I said, my 319 uses the first #3 (276303) and goes the correct way. I guess you could use #3 (276303) for shell edging so that the fold is on the right rather than the left as instructed in the manual for the 288.
Janey - Neat people never make the exciting discoveries I do.