Oh my - to see those things on a machine just makes me want to cry.
I have a bronze plated (copper colored) White Rotary embossed machine from the company's 50th anniversary in 1926 and I'd bet that the original owner put that darn rag on it within
minutes of getting her new machine.
The protective lacquer is completely worn off of that area and there is not any patina - so there's a bright copper stripe all around the arm of this gorgeous old machine.
At least this will mend itself with time. The real heart-breakers are the ones which have decals and japanning dinged to death underneath the rag.