missing letter bicentennial halfs

[Klclark3]

Probably nothing but I got some half dollars today in change, the letters are missing on the back, also on pne there is a faint e with square holes underneath. Please explain, don't be rude

 

[Jack_MIghtyheart]

Looks like a strike through grease error. Pretty common error where there's too much grease on the die and some parts don't get fully struck. Not very valuable unless the coin is missing a large part of the design.