Grease filled die. They are fairly common. Known as "In God We Rust" coins. Not really worth a premium but still kinda cool. I keep all of the ones I run across.
Yes.. It is struck through debris. The letter T on the die was compacted with grease and/or debris and did not allow the T to form on the planchet properly. We have seen a few of these here on CoinTalk. Nothing really major. They call it the.. IN GOD WE RUST Quarter