These is What is Meant by a Mintmark

A mintmark is an identifier on each coin that tells you where that particular coin was minted. It’s a security feature to help curb counterfeiting. So, you would ordinarily try to find the mark that is on each coin. One thing we should be aware of though is that not all coins bear this mark on them and this is because of a few factors.
Sometimes the original mints in a region will mark their coins, and that will be the unique or stand out factor for the coins for that mint. Sometimes, the marks are also just not put on purpose. A good example of this are the Lincoln cents that were minted in San Francisco and West Point mints in the 90s. You couldn’t distinguish these coins from those minted in Philadelphia. There was a problem at the mint of some sort where grease clogged up and the dye had a problem. Some coins were left with no mintmark or a very weak one that was easy to scrape away.
So, if you want to look for the mark, where are you going to look? We are told to look on the obverse of the coin, most times anyway. Sometimes though, the mark can be found on the reverse of the coin. During the Second World War, there was a shortage of nickel used to mint the 5 cent coins (nickels). Due to the shortage, silver was instead used, and the mintmark was put on the reverse side of the coin. This was a distinguisher. The placement of the mark varies from country, mint, coin and sometimes the decision of the people concerned. You will find they can decide to change the position of the mark as they wish, or go without one.