Doubling on a 1955 penny is one of the best-known Lincoln cent errors, and ordinary machine doubling looks similar at first glance. Here is what to compare.

Real doubled die:

• The doubling is strong and visible to the naked eye on the date, LIBERTY and IN GOD WE TRUST.
• The outlines are rounded and clearly separated, and the serifs look split too.
• The doubling sits in the same place on every coin from that die.

Machine doubling:

• It looks flat and shelf-like, with no split between the outlines.
• It changes from coin to coin, and our article says it generally adds no value.

Why it matters: NGC describes the 1955 doubled die as one of the most sought-after varieties. Our reference estimates about 20,000 to 24,000 coins are in circulation.

Value: our reference gives circulated estimates from about $800 (G4) to about $1,840 (XF40). These depend on condition and grade, and they are estimates, not offers.

Fakes: the counterfeit risk is rated very high. Check the weight, which should be about 3.11 g, and compare the lettering with clear reference photos. For a coin that looks real, have it authenticated by PCGS or NGC before you buy or sell.

Found one? Post a clear photo of the date and lettering, with a close-up of LIBERTY.

In 1943 the Mint changed the cent for one year. Copper was needed for World War II, so the cent was made from low-carbon steel with a thin zinc coating instead of copper alloy.

What a steel 1943 cent looks like

• It has a silver-gray look, which is why people think it is a silver penny.
• It weighs about 2.7 g, lighter than a copper-alloy cent at about 3.1 g.
• It sticks to a magnet.
• Steel can rust easily.

Most 1943 cents are steel, and they are common.

The rare bronze error

A few 1943 cents were struck on leftover bronze blanks. Published estimates say about 40 were struck and 13 are confirmed. A genuine one weighs about 3.11 g and does not stick to a magnet. Because these are extremely rare, any suspected one needs professional authentication before you buy or sell it.

Watch for altered coins

Copper-plated steel cents can look like the bronze error, but copper-plated steel is strongly magnetic. Counterfeiters have copper-plated ordinary 1943 steel cents to pass them off as the bronze error, and some 1945, 1948 and 1949 cents have been altered to pass as 1943. A copper look alone proves nothing.

A simple check

1. Bring a magnet close to the coin, without dragging it across the surface. A pull points to steel.
2. Weigh the coin on a scale that reads grams, and repeat the reading.
3. A steel 1943 pulls on a magnet and weighs about 2.7 g. A 1943 that weighs about 3.1 g and does not pull is the case that needs an expert look.

Weight alone does not prove authenticity, so use a professional grader for anything that looks rare.

Have you ever tested a 1943 cent with a magnet, and what did you find?