Rodney,
The W&W 9D was the direct forbearer of the Singer 9W-7. Singer bought out W&W and actually continued production
of the 9D with Singer decals on it. Then not long afterwards Singer made a few changes to make them compatible with Singers cabinets.
I have two of the later Singer 9W-7s and they are excellent sewers. The only odd things is they turn backwards from all other Singers, the earlier ones use a funny doughnut shaped bobbin that is scarce and they take the obosolete 127x1 needles. There is a substitute that works great though.
Joe
I like the two I have and doubt I'll part with them.