Take the paint off first and see if you can tell whether it's brass or silver. If it's silver, you might be able to do it without much damage. Use some vise-grips to hang some weight on the piece, then carefully and evenly heat it up until it drops off. Use a soft flame and don't let it get to red. You'll still have some residual silver to sand down, but a lot less than grinding and filing the whole thing.