Jon Helig is a member here so he'll likely chime in.?
I have a D-9.? See its photo in my "new acquisition" topic thread started on 5/31/22.? There are those here who are way, way beyond me in W&W expertise but if I can help in any way, I'll try.? My D-9 arrived in good shape and didn't require much work.? The previous owner had used the parlor cabinet as a lamp stand and said that he "never dreamed" that anyone would want to buy it to actually sew on it.?
Anyway, I'd love to see a photo of yours.
The only advice I can give right now is to use actual sewing machine oil (smo) for cleaning and lubricating.? Don't use water, windex or other cleaning agents, even on the cast iron surface.? There are several good youtube videos on cleaning antique sewing machines while preserving the decals. ??