Mint Errors are a fascinating, and addictive, field within the numismatic hobby! They make unique and wonderful gifts, for both personal (yourself, family members, and friends) and business acquaintances (Manager/Supervisor, Peer, Subordinate, Team Member, and others)! Mint Errors come in many different types and are caused by many different things in the beginning-to-end minting process.
You as the collector determine whether you want to collect Mint Errors by denomination, by coin series, by date, by type of Mint Error, how many types of Mint Errors, or some combination of these or other collector-defined criteria. You're only limited by your desires (and finances, of course, but that's true with 'most anything). That's one of the beauties and more satisfying aspects of this numismatic field. Another one is that you will probably be the only one on your block, on your street, or in your town that owns these treasures. Yet another one is because of their reason for being - since they are Mint Errors, no two Errors, even within a given type of Mint Error, are identical. Each Mint Error is, by definition, unique, not designed nor meant to be produced as a Mint Error!
Before going any further, I highly recommend that you join "CONECA". That stands for "Combined Organizations of Numismatic Error Collectors of America". You'll be glad you did! Their website is listed on my "Links" page. When you join, tell them Denny sent you.
Be aware that there are "manufactured errors" in many categories. By "maufactured" I mean intentionally mutilated, doctored, and/or faked outside of the normal minting process, indeed outside of the U. S. Mints. Unfortunately there are individuals that "manufacture" them in order to make money without any expense, or the coins have been accidentally altered outside of the mints then some unsuspecting person finds them or gets them in change and thinks they have the genuine article. Don't let this deter you from your interest and pursuit of Mint Errors! Just be aware of it and proceed accordingly.
There are several Mint Error reference books you can buy that will provide the diagnostics necessary to understand the difference between the genuine and the altered, however it occured. If you ever have doubts about something in this regard after using the reference books, I would recommend contacting a reputable coin dealer (myself included here). Many local and regional coin clubs are another good source of this knowledge.
Again, join CONECA. There are many people in the club that are very experienced with Mint Errors. Mint Errors are an extremely rewarding part of the numismatic hobby!
Once you've had an opportunity to peruse and enjoy this basic "Mint Error Education" section of my website, please feel free to check out the Mint Errors that I have for sale (and all other items as well, of course) in my "Inventory" section. Some of those will have pictures, some won't. Some of those will have multiples, some won't. For those Mint Errors that do have multiples, each one is going to be unique due to its reason for being, but in some cases there'll be many examples that are very similar in appearance. In those cases where I have more than one available, I list the "Quantity Available" in the description.
There is also a related field called "Mint Varieties" within the numismatic hobby. The most famous of these is the "Doubled Die" with the most famous of those being the "1955 Doubled Die Lincoln Cent". I don't delve into the Mint Variety field in detail herein. Again, there are some excellent reference books that cover this field of numismatics.
Without further ado, ENJOY!!!!