We have had a discussion previously on this possible error. I just finally found time to get better pictures. The previous discussion was never really settled so maybe these pics will help. I think last discussion hinted towards possible grease fill error.
Yes the missing letters are results of grease filled dies. Also looks like a die dent near unum. Is that a mountain or valley? Got die chip on Washingtons jaw line and below ear looks like.
When a coin is well circulated it makes it a little harder to make this diagnosis. For example if this coin was brand new, there would be no doubt about the missing letters. In this case it could be a greaser, or it could just be worn. As it has been in circulation for over 50 years.
It was a pretty interesting find about a year ago. Still look at often as it was one of my first finds when I started collecting. I have found and learned soo much about coins since.
@Michael K This is why this coin makes a great discussion. I love to learn the different points of view.
@Tyler Graton Its crazy how there is a picture of a 1965 Quarter with almost the same exact errors on the link you sent me. Makes me feel better about my find. Thanks!
The value wouldn't be worth grading the coin just in case you are wondering. . I'd say it would be about 1.50 to 2 bucks for your example. Conservative estimate FYI, that's all I would pay for it.