Sometimes coins have what is called a Struck Through Grease or Struck Through Debris.. The die has some kind of debris and won't allow for some of the letters to form properly when the Blank Planchet is struck. Then a little bit of circulation wear also can make the letters look the way yours does... it is 46 years old!
@Andrew Emil Hurley Please post any future questions if you think you have a Mint Error over at the Error Coins section of CoinTalk... First find out if it's a worthwhile Mint Error or not, then worry about value. Many minor errors don't have any premium
