The stamp appears to be #12e with a value of $45 used in the 2009 Scott catalog.
#10 should have frame lines (note the wide margins in the picture) and a very coarse cross-hatching for the background of the oval.
#11 has no frame lines and a much finer cross-hatching.
#12 has an additional "outline" at each of the corners. Hard to tell with your picture resolution, but it does look like the outline is there. Stamp appears green, hence #12e.
Nice Wytheville, Virginia cancel!
Wytheville today...
http://www.visitwytheville.com/I don't collect Confederate States, but enjoyed the pic! Thanks for sharing!

k