The quick answer is 2.5 mm (about 1/11 inch). Silver Eagles are much larger than silver dollars.

Silver dollars are Eisenhower, Peace, Morgan and Trade dollar coins that are 38.1 mm in diamter and have a face value of $1 and a silver content of about 7/10 of an ounce, although some Eisenhower dollars have no silver content. Most people are familiar with silver dollars.

Silver Eagles are 40.6 mm in diamter (much larger than a silver dollar) and are 1 ounce 99.9% pure silver bullion. Although they are stamped one dollar on the revese side they have a value roughly equal to the silver market, which is currently around $20. A silver eagle has "1 oz. fine silver" printed on it.

Please note that people frequently refer to silver eagles as silver dollars because they say "one dollar" on them. If you are buying supplies to store your silver eagles please be sure to specify that you need silver eagle products since they are much larger than a standard silver dollar.

The simple answer: if you have to ask then you probably should not.

We'll break this answer down into two types of coins. The first type is pocket change. These are coins that you have accumulated over time. They have no particular value and are in less than outstanding condition. Pocket change coins might have a special meaning to you as a collector but probably do not have any significant value over face value of the coin. You can clean pocket change coins with a number of solutions starting with mild soap and water. Make sure that the soap that you use is not a detergent, which can scratch. Rinse your coin in running water and pat dry. Do not rub your coin to dry it since that can also scratch the surface. Additional chemical cleaners are also available for cleaning coins. Before you clean your prized possession you should always test your cleaners on a coin that you are willing to sacafice.

The second type of coin is one that has a collectible value. Perhaps it is old and rare. Maybe you found it in a field or your grandfather's attic. Or, it might have been sitting ignored and tarnishing in a coin album for the last 50 years. In all cases, if your coin has a collectible value we will repeat: IF YOU HAVE TO ASK - DO NOT DO IT!!! What do you have to gain? More importantly, what do you stand to lose. In all cases your lack of knowledge can only devalue your coin. Take it to a coin dealer and discuss your options with someone who knows what they're doing. If in the end you decide that it's a wheat back penny that's only worth 500% of its face value ($0.05 cents instead of $0.01) then maybe you'll consider it "pocket change", in which case you can follow the steps above and accept the outcome.