This is something EVERYBODY should be aware of !! Adding mint marks is one of the most common methods of fooling collectors & dealers alike. This article will help you learn how to identify some of them - Click Here
I don't think I'm going to buy any key date/semi key date mint marked coins in the near future. I don't think I could tell if it was added of not.
Wow GD! That is a very interesting article. I noticed from looking at older coins recently, sometimes the mint mark is a little fatter than on another coin and not quite as defined. Such as the "S" on some of the gold pieces I've looked at. Sometimes the head and tail of the "S" are clearly defined and sometimes they're almost smashed together with the main body of the "S". Is this just because different punches were used or because of different amounts of wear, etc.? Is there any source out there that has what the mint marks should like like on certain varieties of coins? Thanks again for a good article.
It is not at all unusual for the mint marks on any given series to be slightly different. They can be in different locations, they can have different shapes or serifs, they can be clear or blobs etc etc. But most all of these variations are known for the various series of coins. But there is no single book or source that list them all. You have to have the right book for each series. Breen's Encyclopedia will list many of them for the various series but not all of them.
In the past I have turned to computerized authentication to check some 1916-D Mercury dimes and some 1932-S and 1932-D Washington quarters. In each case, I took high quality digital photographs of the coins in question and compared them to photographs of genuine coins with their different mint mark variations. In the case of the coins in question, I was able to determine that one of the 1932-D quarters I had suspected as having an added mint mark did in fact have one. Prior to using this method, I had checked the coin myself and had three other dealers check it as well and their consensus had been then it was genuine! Just goes to show how careful you need to be.
Over the years I have found it amazing just how many collectors have altered or fake coins in their collections and are not aware of it. Often they never find out even after decades of owning them. It is typically only discovered when somebody tries to sell the coins and they have to be authenticated first. The same is true of many dealers when they sell coins. They sell the coins as genuine because they believe they are genuine. The dealers are often completely honest men - they just don't know enough to identify some of the better quality fakes and alterations.
I've only ever heard of a few mistakes and typically they were high quality counterfeits not altered coins. Of course I am leaving out the micro O variety that fooled just about everybody for the past 100 yrs - but they are counterfeit - not altered.
