How Can I Clean Monnaie De Paris Coins?

You cannot. Any attempt made to "restore" them will make them worth much less. Don't touch them (but post pictures!).

Hello and welcome.

How much protection a coin needs depends on what it's made of. With the exception of gold, a piece of raw shiny metal such as a freshly minted coin is not in its natural state in the atmosphere of Earth. From the moment a coin is made, the atmosphere is trying its best to turn it back into the minerals from which it originally came. Some metals react faster than others, but they all will eventually react if left exposed to the air. So basically, anything that keeps the air (specifically, moisture and sulfur in the air) out and does not itself react with the coins should do the job. Unfortunately, some of the cheaper coin albums out there are made from a type of plastic that can actually harm coins.

The little cardboard holders, known as "2x2s" because they are 2 inches square, do a reasonable job for most coins. You can also by more specialist "airtite" coin holders. There are even companies that you can send your coins to who will seal your coin up in a hard plastic case, or "slab", but this is really only worthwhile for expensive coins that can justify the cost.

It also should go without saying: don't touch shiny coins with your bare hands, and don't cough, sneeze or talk over the top of them. Also, try to keep them somewhere where the humidity is low and the temperature does not wildly swing up and down.

Thanks for your replies everyone. So it seems I'm already on the back foot with my coins then. What a shame :( I wish I'd known all this in advance.

I collect the MdP Disneyland Paris coins. I first went in 2010 and thought they were a nice inexpensive souvenir. I only found out that there were a lot of older coins after looking on the internet for one we'd missed getting on our last visit!

So I've since bought some of the older ones on ebay. But it seems a little odd that coins from 2007 or earlier would be still so shiny when not in protectors - unless they were taken out of their protectors to send to me!