Everyone has their own opinion on this subject but it is generally accepted that some collectors do clean their strikes. If you plan on trading them to someone else let them make the decision whether to clean or not. Do not use anything that requires rubbing the silver part of the strike or it will leave streaks, scratches or other unwanted marks. Some collectors use a brass cleaner with a Q-tip on the outer ring but it is not the best way. Some even use ketchup and swear by it but you should experiment on a cheap unwanted strike to see if it works for you.There is a product in the coin stores called e-Z-est that you dip the strike into for a very short period (two seconds) and then wash with water and pat dry. Do not rub the strike they are easy to scratch. Some claim to use e-Z-est and then neutralize it with alcohol and dry it with a fan so they don't have to touch the surface of the strike, I haven't tried this so you are on your own if you want to experiment. If you want to go to the trouble to clean your collection then you should have air-tite capsules to put them in to keep them from tarishing again. There are several of these on the market with and without a foam ring. That is something else to debate.