notsureif,
I know what you mean about the crinkle paint. I've got several machines, 2 Kenmores and a Singer with that paint job. So I'm with you that they must have been offered as new by the factories.
My 66-18 is a -18, so there's no problem for me. The pic posted by Diamond2 is of a 66-18 as far as I can tell.
Joe