Honestly, I wouldn't. Especially if they are old and collectible. Cleaning them will devalue them significantly. Find out what they are worth before attempting to clean.
I agree with Naomie! Yes, find out the value of them first before any cleaning.
A quick story...the mother and father of my boyfriend (years back) had a coin collection and they showed me the coins. The coins were old and tarnished. I took them and shined each and everyone of them up by rubbing them on a section of carpet, needless to say, there went the value of their collection.