I ended up refinishing the outside of the cabinet for the Pfaff 31.

I hand sanded it to remove the old finish, then sanded it just enough more to remove the stain.

The cabinet itself is made of oak and oak veneer.  It was originally stained in walnut to go with the walnut veneer on the front of the cabinet.

Many of the older cabinets were made in the same style and quality as other furniture of the times.  The machines often stood in the living room of the house where it would be seen by visitors, even when not in use.

Later cabinets were made of cheaper materials, though I'm not sure when the change ocurred.  The Pfaff 262 (made in the mid 1960s) that my wife uses also has a good quality cabinet made of oak and oak veneer (though in a lighter color.)

I sanded the old finish off the the Pfaff 31 cabinet by hand because I was afraid of sanding too deep if I used a power sander.  The oak veneer is less than 1/8 inch (3mm) thick - it would be easy to sand through that with the rough sand paper it took to remove the old finish.

I left the walnut veneer alone - I didn't sand it at all.

With the old finish and stain removed, I applied new walnut stain to all of the oak pieces.

I used that bottle of "Fernol" on the walnut veneer.  Fernol is an oil based furniture polish made to clean up and restore old finishes.  It took care of the scratches and the house paint drips on the front of the cabinet.

I applied shellac over the newly stained wood.  I had a half a liter (or more) left over from when I cleaned up my Adler 8 and built its base.

Shellac has a beautiful effect on wood.  No other finish I've seen comes close to making the wood grain stand out so beautifully.

I use the ethanol as a thinner for the shellac.  The shellac I used was a thin "cut," but even so I found I needed to thin it some, else it would dry too fast for me to get an even coat.

The refinished cabinet looks like this:

After the cabinet was refinished and reassembled, I wiped the Pfaff 31 down with the Fernol and reinstalled the machine in its cabinet:

Sewing machines are traditionally cleaned with sewing machine oil.  Wipe on, wipe off.  It leaves a thin film that shines and prevents rust.  You do have to wipe off, though.  My Adler 8 appears to have only ever had oil applied to it without the excess being removed.

I think the results of the refinishing (though far from perfect) were worth the time, especially as compared to this:

My daughter and her boyfriend visited us this weekend.  They took the Pfaff 31 home with them.

She's promised to send pictures of the first completed project sewn on her great grandmother's sewing machine.