As near as I can figure from this post and what you posted on another site when you were looking for an embroidery attachment, this is similar to the zig-zagger attachment that was for the early slant shank Singers. I was surprised to see that they were also made to fit the 15-91, Featherweight, and other "straight" shank machines. I could not find anything with R-W77 Ruby for search terms.
Just can't leave a mystery alone! I think I found it on "Yahoo! Japan" as "* si surreal R-W77 sewing machine embroidery attachment, with RW-77 on the box. Since it is in Japanese and English combined, I am probably missing something (a lot), but WOW!, if that fits an older Kenmore, looks like fun.
Last edited by elnan; 06-11-2015 at 09:13 AM.