I've tried to polish them before (not rare or valuable ones). It's impossible to get in between the lettering and denticles, and you can't get the nicks out without warping the field. Tumbling it will damage it even more. Sometimes at work I would be doing a repair on a coin pendant, be super proud of my work, and then be berated by the boss for not having buffed it. Ever get that feeling when you know you're 100% right but your boss still looks at you like you're a goat? Probably how this seller feels.