It looks like the same thing my mother gave me when she gave me her machine - a Singer 15-91. I was going crazy trying to figure out how to use them. Finally called my mother and asked how they attached to the machine - what was I missing. They weren't in the manual for the machine and the Singer book she gave me. Turns out her mother (who gave her the machine for a wedding present) found them somewhere for a good price and so got them. My grandmother never sewed - my great grandmother (her mother) was a seamstress - so she thought all machines were the same and thought she found a deal. My mom couldn't figure them out, but passed them along (because in my family you never throw anything away that may be useful some day.). When I looked on the back there was a a "W" engraved in the back, so I donated them to a thrift store. I believed that to stand for the "White" machines which at one time were a competitor of Singer. I was kind of sorry that I didn't buy the White treadle when I found it back in '89, but I have a Damascus from my Great Aunt May which I prefer to own.