Oklahoma Quarter missing letters

[magusxxx]

Recieved this out of a roll this weekend. A few months ago I found one with a very Weak D and now this. I know it's probably because they were struck through grease or something but are these worth slabbing?

http://www.ethereal.net/~magusxxx/coinset12/quarter.jpg

[diamond]

Struck through grease, as you say. Not worth slabbing.