Coinsandcanada.com

This is possibly a newbie question, but I'm honestly unsure. If I clean my older coins will they decrease in value?..

Yes, they will reduce in value, but it all depends on the scarcity of the coin, what kind of external source is present on the coin, and if you are just minor dipping or actually cleaning. It's far better to leave everything as is, unless you are dealing with corrosion that will get worse. You need to study the subject and start here by doing an archive search

Thanks Bill