It should not hurt the value on these, as they are a common set of wings. In general though, it depends on who's buying them. Some collectors keep them shined up, many others like the original patina. Luckily it is a set of wings and they are kind of an exception to the rule of "never clean anything" when it comes to many areas of collecting, militaria or otherwise. Besides the fact that wings were kept polished anyway during their active use. Any pilot worth his salt wouldn't be caught dead with a dirty pair of wings on, so in that respect it's all good. On the other side of the coin, cleaning is not something I like to do to any historical object unless it is needed for preservation. The more you clean a silver object the more silver you lose. I'm not talking about the silver value, i'm talking about the details of the piece. High points get worn down, details get rubbed away, scratching is possible, etc., etc.
