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If the Lincoln Memorial penny has a date before 1982, it is made of 95% copper. If the date is 1983 or later, is made of zinc-plated 97.5% and with a thin copper coating.
For penny minted in 1982, when both were made of copper and zinc cents, the safest and best way to tell their composition is to weigh. Penny copper weigh 3.11 grams, while zinc cents weighs only 2.5 grams. Be sure to use a scale that is accurate enough to detect the tenth of a gram (0.10) or better. If you weigh one penny of zinc on a scale that only can record full 1 gram increments, penny displays usually 3 grams, since the scale rounds the hundredth of zinc 2.5 grams up to 3. The wrong kind of scale can be misleading, when you are trying to sort of copper and zinc cents.
If you do not have a scale of gram tenth practice, you can use the proof of "fall". You need a hard surface of Ant, a popular penny of copper and zinc known one penny. Drop each on the table, listening to his distinctive sound. Hundredths of zinc have some sort of a dish "ones", whereas copper Penny have a tone higher, more melodious "ring" sound. Once you have a good feel of how each type of sounds, start deleting one of your 1982 at a time, listening to the sound they do and should be able to order off the metal composition. Of course, this test is not reliable as weighing, but it should help you sort most cents of copper and zinc.
Caution: use only the drop test on circulating cents where you are sorting of copper and zinc for only the value of the metal. Never drop-collectible coins Uncirculated or test in this way to test them, because deleting cents on a hard surface may cause minor damage that can make a collectible coin less valuable.
Tip of Cherrypicker-Watch out for errors of mint "transitional"! On the Lincoln Memorial Cents, "Transient" errors occurred when the Mint accidentally used whitespace copper penny 1983. These cents "wrong stock" weigh 3.1 grams, instead of the zinc 2.5 cents. If you find a copper 1983, just might be useful ... a pretty penny!
