Yes we have seen these before. And no it's not worth sending in. The missing number 1 is due to a issue called debris filled die. That's when an area of the die is filled in and when the blank planchet is struck it will appear faint or not at all. Worth 1 Cent
As others have said, it really doesn't have any additional value in that condition, but it is still an interesting find. I would save it if I found it
Why A.D. 951? The coin may be from 951 B.C., which would make it a 2,967 year old Lincoln cent, much more rare and much, much more dangerous. So: https://en.wikipedia.org/wiki/950s_BC
But how would/could they know about that fella for whom the numbering system was devised? That would be DOUBLED incredible foresight.