I just recently purchased my second Singer Featherweight manufactured approx Oct, 1949. The machine was very nice and it sews beautifully but it and the case smelled so badly that since it arrive three weeks ago it has not been in the house.
I tried everything to get the order out of the machine and the case. After much cleaning of the machine by soaking in a Kerosene bath for two days and spraying WD 40 in every crevice I could find, I finally got the machine odor free but the case...that was a different matter.
I washed the case down with a solution of colorox and dried it throughly, I let it bake in the sun, the hot Arizona sun, for two weeks, I filled it full of Kitty Litter and let it bake in the sun...nothing took away the foul odor
Finally after some research I found it was probably the glue that they used back then to attach the cover and the linings. It could have been a glue made from animals, it got damp and then molded.
So after searching the web I found that a woman actually too all her covering off (the same reason it smelled so badly), and she found a beautiful hardwood tongue and groove box.
So I started two days ago ripping off the cover, ugh, a nasty jog. Make sure if you decide to attempt this, you do it outside. You do not want possible mold spores in your home. I did not find any but who knows what we can not see. Here is how the box looked once I ripped everything off.