I went to the Singer site and looked up my model numbers. One K405712 and it was listed as a class 27. The other a Singer Red Eye G6792274 was listed as a class 15. When I printed No. 15 Instructruction Manual it was for an oscillating shuttle. But when I printed the manual for a #66 it looks exactly like my #G6792274. Sorry to be so dense but I need help I have another S/n K405712 so I printed the instruction manual for a 127-3 & 128-3 with vibrating shuttle. It's still at the repair shop and I can't remember what kind of bobbin it has.