If you have a 1943 penny that looks like it is made out of copper, this is how you can authenticate it to tell if it is a genuine 1943 copper penny, or a fake 1943 copper penny. But first of all, be aware that the 1943 penny was issued in zinc-coated steel, because the USA needed copper for the war effort. Any genuine 1943 copper pennies are extremely rare mint errors. Learn more about your silver colored 1943 steel penny. Compare the dates on the overlay and note that the date on a genuine 1943 copper penny will look the same as a steel 1943 penny, not like an 8 which has been cut in half.
The easiest way to tell if your 1943 copper cent is merely a copper-plated steel penny is to test it with a magnet. If the magnet sticks to the penny, it's made of steel which has been dipped or plated in copper. Such a penny is worth about 15 cents as a novelty item.
If your 1943 copper colored penny doesn't stick to a magnet, then look at the date carefully (using a magnifying glass, if possible.) If the tail of the 3 doesn't extend well below the "line" of numbers, it is probably a cut-in-half 8. A very common fraud involving the copper 1943 cent is to cut away part of the 8 in the date of a 1948 penny. If the 3 in your date looks like half of an 8, your coin is not a genuine 1943 copper penny.
Any time you have a potentially valuable coin, it's always a good idea to take it to a qualified coin dealer for a professional opinion. Most dealers do not charge to have a look at your coins and give you an informal verbal appraisal.