What do the markings on a wheat penny mean underneath the date?

Here is a 1941 Wheat Penny with a “D” underneath the date:

 

And a 1924 wheat penny, also with a “D” under the date:

And here is a 1970 penny, NOT A WHEAT, with an “S” under the date:

 

All of those letters are Mint Marks, indicating where the coin was produced.

Mint marks that appear on US coins include:

  • C: Charlotte (Gold only, 1838-1861)
  • CC: Carson City (1870-1893)
  • D: Dahlonega, Georgia (Gold only, 1838-1861)
  • D: Denver (1906 to date; easily distinguishable from Dahlonega because of the different timeframes in which the mints operated)
  • O: New Orleans (1838-1909)
  • P: Philadelphia (Silver “Nickels” 1942-45; Dollar coins 1979 to date; other coins except cents 1980 to date. Although the Philadelphia mint has been operating continuously since 1793, most Philadelphia coins do not have a mintmark)
  • S: San Francisco (1854 to date. Now mints collector coins only. The last circulating coin to bear an ‘S’ mintmark was the 1980-S SBA Dollar)
  • W: West Point (1983 to date; collector coins only)

(This list and a complete history of mint marks available from the Heritage Auctions Website).  Link will open in new tab.

Pennies without any mint mark were produced at the primary production plant (“ US Mint”) in Philadelphia. When collecting pennies, it is typical to have one from each mint for every year.

history of the us mint ans it's coinage, Amazon

History Of The United States Mint and Its Coinage, from Amazon Books

US Coins 2017

A Guide Book of United States Coins 2017: The Official Red Book, Spiralbound Edition, from Amazon Books

Here is my list that I use when going through my Pennies (I put them in a jar at the end of the day, and sort through them every once and a while; sometimes you find some “keepers”)! Tip: If you click on it, the image will open in a new page, and you can print it, to keep near the penny jar!

printable penny watch list

And when you find some collectible pennies, just wipe any dirt off them with  special coin cleaning cloth (an old sock), and put them in a “flip”, coin book or folder.  If you want to get a child or teenager into collecting, you can get them a whole kit from Amazon or eBay.

Pennies are a little more complicated than they seem, for what we know as common pocket change!

And that is why you are reading: “Pocket change Riches”.

I hope you found my point of view enlightening and informative.  Consider sharing it!
The Last Word:

Is there a special term for a blank coin, before the image is struck?

Planchets ready for minting

Definition: planchet is a prepared disc-shaped metal blank onto which the devices of a coin image are struck or pressed. The metal disc is called a blank until the time it passes through the upsetting machine which causes the rim to be raised. Once it has a rim, the disc is called a planchet.

The phases of a coins beginnings!

When referring to ancient coins, and coins which were made from cast metal discs rather than machined metal discs, the generally preferred term is flan.

 

There are really no hard and fast rules about the usage of these terms in ancient coin collecting, and you will sometimes hear ancient coin blanks referred to as “planchets”, even though they were made from cast metal.    In modern machine-made coinage, the distinction is very clear: the disk is a stamped metal “blank” before getting the rim, and a “planchet” afterwards. A coin that is ready to be stamped is a “Blank” or a “Slug” – From What is a Planchet? from About.com


When the coin is struck improperly, and gets into circulation – the resulting coin is usually prized by collectors as a Mint Error,  and may be very valuable.
Example of Mint error – US cent struck off-center.
Whenever you empty your pockets, check your change – you never know what riches are passing through your pockets!
I hope you found my point of view enlightening and informative.  Please share and repost!  Thank you!
The Last Word:

Why is the cost of production of US coins relatively much greater than other currencies?

cost of production of US penny and nickel
By Alan Chenkin, Novice coin collector and hobbyist

US coins are backed by the might and presence of the US government. The US Mint produces all the coins and distributes them through regulated channels, and at high security.

In the UK, according to the Royal Mint: ”

The cost of producing United Kingdom coins varies according to the specification of each denomination. The value of metal in each coin accounts for a large part of the total cost, but it is also necessary to take into consideration the broader costs of the manufacturing process. These vary according to the complexity of the coin.  The Royal Mint does not reveal exactly how much it costs to make specific coins as such information could be used to its competitors’ advantage.”

While there is speculation that mints worldwide have similar issues to the US, I will focus on US coins.  It is generally acknowledged that the mint spends more on manufacturing pennies and nickels than than they are worth.

The coins (and notes) are minted to be as unique and resistant to copying as possible. As such, many of our minted coins are made of valuable metals vs. cheap alloys. sometimes these metals exceed the value of the coins. Even “cheap” metals, like zinc (used as a filler to reduce the copper content in a penny) have increased in cost over time.

Production is in the US, by Federal employees, paid on government pay grade. Private companies and other governments may be able to produce cheaper coins, but these are not backed fully by the US Government…

Penny Manufacture Cost – verified by Snopes
US Coins have a lot of detail (detail = expense) to prevent counterfeiters and criminals from stamping out copies of US Coins.  This extreme attention to detail (like seeing President Lincoln sitting in the Lincoln Memorial – see penny below) is visible under magnification.  “The Lincoln cent (or sometimes called Lincoln penny) is a one-cent coin that has been struck by the United States Mint since 1909. The obverse or heads side was designed by Victor David Brenner, as was the original reverse.” – From Wikipedia
If you click on it, the penny image will open in a new tab, and you can magnify it further using your browsers zoom settings.
You can tour the US Mint in Philadelphia and see how most coins are made.  I have been there, and it is an impressive operation.  In addition to the minting operation, debate about the design, the artist, and size considerations may take years.  Take a look at How new coins are designed.
If the US goes to all this effort to make a penny unique and secure, you can see we take our coinage seriously.  And it is not cheap! 
Thank you for reading my Blog! – feel free to share!
Edited and expanded from my Quora answer
The Last Word: