Recently picked up this cover. I've tentatively ID'd it as Scott 11, mostly because of the date of use - 1857.
Two questions for our resident experts.
(1) What plate would this be? It has a recut outer left line.
(2) Is it correctly ID'd as Scott 11. It has only the four outer lines, making it Type I, but that is about as far as my knowledge will take me.
Here's the cover and a higher 600 dpi image of the stamp alone.

