It's fun to work on an old machine! The worst one I've ever found was a Belvedere Adler 950-B, coated with nicotine several decades old. It was in a solid walnut table table someone had coated with thick, thick paint. If they had only washed the dang thing before they painted it, it would have saved them a lot of paint! LOL I used a citrus stripper to remove the paint and the smell of nicotine overpowered the citrus stripper! Yuck!
It's now restored and lives in my sewing room. It makes beautiful stitches.