I think you're dealing with 75 year old aluminum corrosion.  Acetone won't fix that. I have dealt with the same thing with no luck so far. If you dont have a special pair of exact fit pliers, you're pretty much screwed, unless someone else has a better solution. I do have the knurled rings for sale on ebay, but you'll need to come up with a way cut the old ring off. Very carefull die grinder work to cut the ring only may work. I also have some of the more common recepticales listed. I may have an odd receptacle in the junk box as well. You may only have to weaken the ring in order to remove it. If I have the receptacle, then you can cut through both and replace both.