Singer never sold anything "blackside". It's a name collectors came up with to call the dark finish that Singer put on items instead of the nickel finish. Speculation is this was done during ww2 when raw materials were scarce. As Singer ran out of nickel finish items, they produced dark finish items. But they were not sold with any particular machine. It is fun to work at putting together a set of "blackside" attachments, but Singer would never have sold them as a set like that.