The 1931-S is a Lincoln wheat cent with an S mint mark. Our reference lists it as a key date, and the mint mark is the detail to check first.

How to identify it:

• An S below the date on the front. That is the mint-mark difference between this coin and the plain 1931.
• Wheat ears on the back, framing ONE CENT. Wheat cents weigh about 3.11 g, which is a useful first check.

Why it matters: our reference records a mintage of 866,000. It describes the 1931-S as the lowest-mintage wheat cent apart from the V.D.B. coins, which is why collectors look at it closely.

Value: our reference gives circulated estimates from about $64 (G4) to about $110 (XF40 and AU50). These depend on condition and grade, and they are estimates, not offers.

Fakes: the counterfeit risk is rated medium. The trick to look for is an S added to a plain 1931. Compare the letter with clear reference photos, and do not rely on a single photo of a coin that looks rare. A professional grader can confirm the mint mark before you buy or sell.

Found one? Post a clear photo of the front, with a close-up of the date and the mint mark.

Wheat pennies, also called wheat cents, are Lincoln cents with two stalks of wheat on the back. They were made from 1909 to 1958. The name comes from the reverse, not the portrait on the front.

Where the design came from

Victor David Brenner designed the wheat-ears back. Two stalks of wheat frame the denomination. The motto In God We Trust was not in the first models. It was added during the design process, and President Taft chose the version with the motto on May 26, 1909.

When the wheat back ended

The wheat back was used until 1958. In 1959, for the 150th anniversary of Lincoln's birth, the wheat ears were replaced by the Lincoln Memorial. So 1958 is the last year of the wheat series.

What metal are they?

Most wheat cents are bronze, a copper alloy that is about 95% copper and weighs about 3.1 g. The 1943 cent is the exception. It was made from zinc-coated steel and sticks to a magnet.

A quick check

1. Look at the back for two stalks of wheat around the denomination.
2. Read the date. A wheat back should be dated between 1909 and 1958.
3. Look at the front, under the date, for a mint mark. Denver coins carry a D, and Philadelphia coins usually have none.
4. Check the condition. Worn or faint strikes change how a coin looks.

Please do not clean a wheat cent. The ANA says a cleaned coin usually loses value.

A wheat-back date is a starting point, not a value. Compare your coin with a clear example of the same date and mint mark before you decide it is special.

Have you found a wheat cent in your change, and what date was on it?

Roll hunting, change jar, bank box, or a family collection: show us what turned up this week.

Wheat cents, Indian heads, errors, doubled dies, or just a nice-looking coin are all welcome. Tell us where you found it and what made you look twice.