I have 3 myself. I didn't realize there was a site on this board dedicated to Featherweights. I got all my information several years ago from another group called Featherweights I think. They said the smell from the case came from the type of glue that holds the fabric to the box. It molds or something. There were a lot of recommendations on there too, same as I was reading on here--soap, charcoal, lots of lot sunshine, etc. One recommended suspending a low watt light bulb in the case for days, not sure of the specifics now. Thanks goodness my cases did not smell that bad. Love my Featherweights, though. I am getting ready to put my Singer 401 up, use the 500 Rocketeer for a while, then switch to a Featherweight. I go back and forth between them because I love using all of them so much!
Joyce