Cleaning Coins

i have old cions ...can you tell me the history of each coins ?

I agree 100% with biokemist. For those who are thinking about cleaning their coins, I cannot recommend rubbing with ANY type of cloth or using baking soda or other harsh methods. These classic methods will cause permanent damage to your coin rendering it cleaned for life.

I had a British farthing (bronze) from Victorian era, it was in a big mess; verdigris, dirt and don't remember what else. I soaked it in olive oil and after a couple of days I was very impressed with the results. So did I made a wrong move? Should I have left the coin as it was? It looked more like chiouaoua pooh than a coin. Isn't olive oil safe for bronze/copper coins? Especially if they are in big mess? As far the velvet cloth, I have successfully removed fingerprints from proof coins, ofcourse I only wiped the problematic area very gently.

As noted any type of rubbing with almost any material will create scratches and although small, they are accumulative. The more you rub, the more scratches are created. Sort of like the River that created the Grand Canyon. Slowly, but completely wear away the coins.
The problem with using Baking Soda and water is really wrong. Not all Baking sodas are the same and for sure water everywhere is completely different. You must remember that in many homes the tap water is either Fluorinated, Chlorinated, run through a water softener and just full of STUFF. For example most people with house plants know you should not use tap water for plants until it has set for 24 hours to allow those gasses to excape.Well water is even much worse with things that should not come in contact with coins. Spring waters too contain miscellaneous different items.
So mixing Baking Soda and water could, may, might, be a real different reaction for some compared to others.
May well just use a brass wire wheel and make them all pretty and shinny.