How Can I Tell Coin Composition?

By far and away the easiest way to find the metal composition of a coin you are unsure of, is to identify it with the assistance of a catalog.

To help yourself to get to the catalog entry that will tell you, visual identification by way of designs, incriptions, dates, color and edges to look for core material, will speed you to the catalog entry.

Passing a magnet over the coin will also help. Pure nickel, iron and steel are magnetic.

For this exercise, I have found that the Krause books are the best.

If you have a coin made both in silver and (cupro)nickel, the silver coin will either be heavier or thinner. Most of these coins are rather big. If you have another coin in approximately the same size, which composition is known, you should be able to tell the difference in weight or width by comparison.

Probably the one sure way is as noted already. Get catalogs or other books on those coins that explain exactly and to what extent a coin was made. All other tests are just to vague and chancy.

Your real problem is copper and brass or bronze. In most cases there is no real information on what the specific composition used was. Brass can cover a very wide range of alloys and a wide range of color. And some alloys of brass can be very hard to tell from bronze or copper. A cleaned copper coin can also look like brass. Sure if they use a 30% zinc 70% copper brass alloy you will be able to tell but a 5% zinc and 95 percent copper can tone to a nice chocolate brown. (This is the alloy used for Lincoln cents from 1962 to 1982. Take a look at a group of cents from that era and you will see a wide range of colors.)

So color won't work and neither will weight or specific gravity. There is no way to definitely tell them apart using equipment that the average, or even above average collector will have access to.